Physics question

[cheesemethod]

Does anybody remember that thing in high school called physics? Perhaps you can help me then.

Does adding weight effect the maximum velocity of a self propelled body in atmosphere?

Imagine it this way. You have two identical cars, side by side on a flat straight piece of road. The cars have identical shapes, identical power, identical everything. Now place a 100kg weight into the boot of one of the cars. Obviously once they set off, the car with no weight in the boot will accelerate faster. But, will this 100kg extra have an effect on the top speed of the weighted car - will it be able to achieve the same top speed?

[steve_t]

Pretty sure it's a no. The power of the car has only to overcome the resistance afforded by the air and the tyres. If the added weight created more drag on the tyres then yes.

[Mully]

But doesn't the extra weight affect the effect of gravity on the car?

[R6_kid]

Pretty sure it's a no. The power of the car has only to overcome the resistance afforded by the air and the tyres. If the added weight created more drag on the tyres then yes.

This would be my guess too. For an aircraft it would not be able to reach the same speed in straight and level flight as it needs to generate more lift to overcome the extra weight - same idea with a the car - more weight = more surface area and more pressure on the tyres = more resisitance to overcome.

[LBD]

But doesn't the extra weight affect the effect of gravity on the car?


Identical everything he said, I would assume that includes rolling resistance. When he says weight he probably means mass...so if both options have the same rolling and wind resistance, then there would be no difference in speed

[el_scor_cho]

gunna go with a no also. but i think in your eg the car with the weight wont reach the same top speed as the one without.
i think the space question depends entirely on aerodynamics restricting the two objects when they reach max v

[nothingflash]

Perhaps - I reckon the impact of added weight will affect acceleration more than top speed. Of course if you chucked them both out the side of a plane the heavier car will get there first.

[Big Dave]

Theoretical extra Mass doesn't limit maximum velocity but requires greater force - or more time - to achieve it - and to stop it.

Real world and it all runs out of puff. Friction in supporting the weight etc.

[Big Dave]

Of course if you chucked them both out the side of a plane the heavier car will get there first.

Galileo proved otherwise.

[KiwiGs]

Weight makes little difference to terminal velocity, it just takes a longer distance to achieve top speed for a heavier vehicle with the same power.

[steve_t]

Perhaps - I reckon the impact of added weight will affect acceleration more than top speed. Of course if you chucked them both out the side of a plane the heavier car will get there first.

Get a 50kg chick and a 120kg dude to go skydiving. Get the chick to powerdive and the guy to adopt the normal skydiving 'sprawl' (I have no idea what it's called). I guarantee you that the less-than-half weight wee girl will get to the ground faster ;)

[nothingflash]

Galileo proved otherwise.

So if I throw a feather and a 1988 Mazda 323 S/W (with one careful owner) out of a plane the Mazda won't win?

EDIT: Depends from what height I suppose - anyway...

[CookMySock]

No.

There are two forces, one accelerating the object, and the other is the friction force of it moving through the atmosphere.

Assuming the force accelerating the object is constant, as speed increases friction force also increases until the two reach a zero algebraic sum. Accelleration ceases - the object reaches equilibrium - two constant but opposite forces..

Steve

[ducatilover]

Galileo proved otherwise.

I think I learned that during my kindy and nappies times:shutup:

[ducatilover]

So if I throw a feather and a 1988 Mazda 323 S/W (with one careful owner) out of a plane the Mazda won't win?

EDIT: Depends from what height I suppose - anyway...

We are talking about objects with the same co efficient of drag here...not jappa cars and dead chicken bits

[p.dath]

p=mv

where:
p=momentum
m=mass
v=velocity

If all other factors are the same (as you say they are), meaning the momentum remains constant, then if the mass increases the velocity must decrease.

[steve_t]

So if I throw a feather and a 1988 Mazda 323 S/W (with one careful owner) out of a plane the Mazda won't win?

EDIT: Depends from what height I suppose - anyway...

The Mythbusters guys dropped a feather and a bowling ball in a vacuum and, yes, they fell at the same rate. A feather only falls slower due to the 'wind resistance' it has.


p=mv

where:
p=momentum
m=mass
v=velocity

If all other factors are the same (as you say they are), meaning the momentum remains constant, then if the mass increases the velocity must decrease.

2 objects travelling at the same velocity with different mass have different momentum. This doesn't mean their terminal velocity is different

[p.dath]

e(k)=1/2 mv^2

where:
e(k)=Kinetic Energy
m=mass
v=velocity

Assuming both engines can put out the same amount of energy, then once again, if mass increases velocity must reduce.

So on several levels, if you increase the mass the velocity must go down.

[steve_t]

e(k)=1/2 mv^2

where:
e(k)=Kinetic Energy
m=mass
v=velocity

Assuming both engines can put out the same amount of energy, then once again, if mass increases velocity must reduce.

So on several levels, if you increase the mass the velocity must go down.

Best to consider the skydiving analogy again

[crazyhorse]

This is the very reason I left school - :whocares:

[Morepower]

Best to consider the skydiving analogy again

but the aerodynamics was different. If both cars are equal in every way than the heavier car will be slower , even if its only slightly.

As Scotty says , You canna change the laws of physics captain

[LBD]

Galileo proved otherwise.

Galeleo or Newton?

Two articles same shape and density but diffferent sizes, accelerate and fall at the same rate. Two articles same size and shape, but one of greater mass will fall at different rates, if falling through the same atmosphere....

[RDjase]

The Mythbusters guys dropped a feather and a bowling ball in a vacuum and, yes, they fell at the same rate. A feather only falls slower due to the 'wind resistance' it has.


Adam and Jamie have a great job on MythBusters aye, and there never short on explosives:Punk:

[steve_t]

OK, I googled it and there are some pretty big formulas given by some physics guys. They also agreed that the max speed for the heavier car will be slightly less (1-2mph (that's their units, not mine, I'm km/h)) but only due to increased drag in the tyres, bearings, and drivetrain.
Feel free to google it yourself
As crazy horse has said :whocares:

[crazyhorse]

Yahhhhhh..... Go Steve_T :Punk::Punk::Punk::Punk:

[p.dath]

Galeleo or Newton?

Two articles same shape and density but diffferent sizes, accelerate and fall at the same rate. Two articles same size and shape, but one of greater mass will fall at different rates, if falling through the same atmosphere....

But these objects are not being accelerated by gravity alone, so this does not apply in this case.

In this case the energy is being supplied by an engine. I've assumed the energy output of the engines remains constant in both cases (since that was what was said). If the energy output remains the same, then the two vehicles will not accelerate at the same rate.

[Big Dave]

Galeleo or Newton?

Two articles same shape and density but diffferent sizes, accelerate and fall at the same rate. Two articles same size and shape, but one of greater mass will fall at different rates, if falling through the same atmosphere....

Galileo.

9.80665 meters per second per second at seal level. Grape or grapefruit.

[The Stranger]

This is the very reason I left school - :whocares:

We have a winner!

[p.dath]

9.80665 meters per second per second at seal level. Grape or grapefruit.

But the two cars are not falling. The acceleration at the earth's surface has nothing to do with this issue.

These two vehicles are being propelled along a straight line along the earth's surface under their own power.

Terminal velocity will occur when the energy output of the two engines is effectively matched by the energy loss caused by wind resistance and friction.

[Big Dave]

But these objects are not being accelerated by gravity alone, so this does not apply in this case..

Crossed purposes - some are meaning dropping from the plane - the plane.

you're still driving to the airport.

[LBD]

Galileo.

9.80665 meters per second per second at seal level. Grape or grapefruit.


Zackerly...close to the same density and shape just different size.

[steve_t]

But these objects are not being accelerated by gravity alone, so this does not apply in this case.

In this case the energy is being supplied by an engine. I've assumed the energy output of the engines remains constant in both cases (since that was what was said). If the energy output remains the same, then the two vehicles will not accelerate at the same rate.

OK, engine vs gravity. Both are constant forces at terminal velocity. Both forces only need to battle against resistance to maintain the object's current state.
Your kinetic energy equation tells you how much energy the object possesses. If a 500kg car and a 2000kg car were both travelling at 50km/h, the equation tells you that the heavier car has more energy, and will do more damage when it hits the brick wall. It doesn't tell you what energy is required to maintain velocity
Where's Crazyhorse again?

[crazyhorse]

But the two cars are not falling. The acceleration at the earth's surface has nothing to do with this issue.

These two vehicles are being propelled along a straight line along the earth's surface under their own power.

Terminal velocity will occur when the energy output of the two engines is effectively matched by the energy loss caused by wind resistance and friction.

I think you need to realise you are beaten on this one :rofl:

[p.dath]

Crossed purposes - some are meaning dropping from the plane - the plane.

Only in simple Newtonian physics in high school would you consider them to fall at the same rate.

In a falling case then terminal velocity will be reached when the kinetic energy being used (or the potential energy being lost - depending on your perspective) matches the energy being lost through wind drag and friction.

[Big Dave]

Zackerly...close to the same density and shape just different size.

Wouldn't matter if it was a cannon ball (as Galileo used). Acceleration due to gravity (without wind resistance) is a constant.

[Indiana_Jones]

Does adding weight effect the maximum velocity of a self propelled body in atmosphere?



Your penis will explode.

And not in the good way.

-Indy

[LBD]

But these objects are not being accelerated by gravity alone, so this does not apply in this case.

In this case the energy is being supplied by an engine. I've assumed the energy output of the engines remains constant in both cases (since that was what was said). If the energy output remains the same, then the two vehicles will not accelerate at the same rate.

Back to the original question.... acceleration is not in question...maximum speeds of the two cars is the question. The both will be the same, if power to propel, rolling and wind resistance are the same....mass (weight he said) will make no difference.

[p.dath]

OK, engine vs gravity. Both are constant forces at terminal velocity. Both forces only need to battle against resistance to maintain the object's current state.
Your kinetic energy equation tells you how much energy the object possesses. If a 500kg car and a 2000kg car were both travelling at 50km/h, the equation tells you that the heavier car has more energy, and will do more damage when it hits the brick wall. It doesn't tell you what energy is required to maintain velocity
Where's Crazyhorse again?

If you talking about an object leaving the atmosphere, or falling from a great height like a plain, then gravity is not constant. It gets stronger as you approach the earth's surface.

Ek=1/2 m v^2

If you know the kinetic energy and the mass, then you can calculate the velocity.

[Big Dave]

Only in simple Newtonian physics in high school would you consider them to fall at the same rate.

In a falling case then terminal velocity will be reached when the kinetic energy being used (or the potential energy being lost - depending on your perspective) matches the energy being lost through wind drag and friction.

The premise of wind resistance was stated. The rate of acceleration remains 9.8m/s/s without it.

Got yer bonce around this one?
http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

[p.dath]

The premise of wind resistance was stated. The rate of acceleration remains 9.8m/s/s

Got yer bonce around this one?
http://www.grc.nasa.gov/WWW/K-12/airplane/termv.html

The rate of acceleration at the earth's surface - yes. If your trying to calculate the terminal velocity of an object either leaving the surface or approaching it then you need to use something like:

F=1/2 G m1 m2 / r^2

It's hard to write it out in text form.

m1 is the mass of the earth. m2 is the mass of the object escaping from earth. r is the distance between the mid point of the masses. G is the gravitational constant.

One you have the force being exerted you can use:

f=ma

where m is the mass of your object. a is the acceleration - which will vary depending on r above.

[The Stranger]

If you talking about an object leaving the atmosphere, or falling from a great height like a plain, then gravity is not constant.

Ok, I'm confused, what is a large area of flat land doing falling from a great height anyway?

[p.dath]

So I guess if you want the terminal velocity going "up or down" you need to consider that acceleration of the falling/rising body will vary.

If you consider the object to be "flying" horizontally then vertical acceleration will remain constant at 9.8 m/s/s, but because it is moving horizontal the vertical acceleration of gravity wont have a bearing.

[Big Dave]

Ok, I'm confused, what is a large area of flat land doing falling from a great height anyway?

Symptom of living on a massive fault line.

[Metalor]

I won't affect the top speed, but will effect the acceleration.

Those comments about a feather vs. a car falling from a great height:

The only reason the feather falls much slower is because the surface area to weight is much, much larger, so it feels more force (due to friction moving through air) PER unit of mass. If the went to the moon and did the same thing we would see the feather and the car reach the ground at the exact same time (provided the were dropped from the same height.)

[Virago]

Galileo.

9.80665 meters per second per second at seal level. Grape or grapefruit.

Yeah, but where exactly is the seal? And wouldn't he prefer fish?

[p.dath]

Consider this extreme case. You reach escape velocity. You are now in outer space. Gravity is now zero. There is no longer any gravitational acceerlation acting on you from earth. The reduction in the gravitational acceleration you experience decreases as you get higher.

The gravitational acceleration you experience while approaching your terminal velocity (assuming you are heading "up") has the same issue. The higher you get, the less of it there is.

[steve_t]

I won't affect the top speed, but will effect the acceleration.

Those comments about a feather vs. a car falling from a great height:

The only reason the feather falls much slower is because the surface area to weight is much, much larger, so it feels more force (due to friction moving through air) PER unit of mass. If the went to the moon and did the same thing we would see the feather and the car reach the ground at the exact same time (provided the were dropped from the same height.)

Aren't u studying Physics Metalor?

[mossy1200]

Back to the original question.... acceleration is not in question...maximum speeds of the two cars is the question. The both will be the same, if power to propel, rolling and wind resistance are the same....mass (weight he said) will make no difference.

Originally talking of 100kg in boot it may be possible the weighed car may go faster because the extra weight on the driven wheels(assuming rear wheel drive)will provide less wheel slip therefore the same wheel speed will provide faster true travel speed.
Just thought I would spanner in the works.
Also assume the tyres have increased inflation in weighed car to offset increased drag on tyre to road.

[Big Dave]

So I guess if you want the terminal velocity going "up or down" you need to consider that acceleration of the falling/rising body will vary.

If you consider the object to be "flying" horizontally then vertical acceleration will remain constant at 9.8 m/s/s, but because it is moving horizontal the vertical acceleration of gravity wont have a bearing.

And back on the flats (well, slightly rounds) did we consider that the vehicles weight decreases as the velocity increases.

If you go fast enough horizontally you'll eventually leave the planet and fly off into space. Some people see this as a goal.

[Big Dave]

Yeah, but where exactly is the seal? And wouldn't he prefer fish?

Arf arf arf. I did spot that and correct on second read - bit fishy though.

[p.dath]

Originally talking of 100kg in boot it may be possible the weighed car may go faster because the extra weight on the driven wheels(assuming rear wheel drive)will provide less wheel slip therefore the same wheel speed will provide faster true travel speed.
Just thought I would spanner in the works.
Also assume the tyres have increased inflation in weighed car to offset increased drag on tyre to road.

Haha. I love your thinking!

It might affect initial acceleration and velocity, but hopefully the wheels would achieve the same level of traction over the time it tacks to reach their respective terminal velocities.

But then again, if the heavier car runs out of fuel quicker ...

[Metalor]

Yup.


Was just reading a comment on terminal velocity.

Terminal velocity is maximum velocity falling under the force of gravity where the object is no longer accelerating due to frictional forces from the air equaling the downward force of gravity but in the opposite direction.

p.dath was right when he said the car with the extra mass in it would have a higer terminal velocity. IF the added mass was 100kg, this translates to a downwards WEIGHT force of 9800 Newtons, so with the same cross-sectional area the heavier car would have to be falling faster in order for the frictional force from the air to equal(and opposite) that of the extra weight.

Sorry, hard to explain without diagrams.

[Big Dave]

Originally talking of 100kg

It was probably drugs too.

[Big Dave]

Sorry, hard to explain without diagrams.

I posted link to NASA's - #39

[mossy1200]

Haha. I love your thinking!

It might affect initial acceleration and velocity, but hopefully the wheels would achieve the same level of traction over the time it tacks to reach their respective terminal velocities.

But then again, if the heavier car runs out of fuel quicker ...
Which car is the STIG in again???My monies on Stig and you can have Jeremy Clarkson......

[p.dath]

Which car is the STIG in again???My monies on Stig and you can have Jeremy Clarkson......

Jeremy Clarkson always cheats ... so I feel pretty safe.

[ducatilover]

Chuck Norris would win

[Big Dave]

Chuck Norris would win

If I let him.

[Big Dave]

And I preferred Biology & Chemistry anyway. You got to burn shit in Chemistry.

[ducatilover]

If I let him.

You have no choice, CN =BD-PWND basically :innocent:

[Big Dave]

EDIT: Depends from what height I suppose - anyway...

Missed this one - i think yes correct - and no - it depends what set of circumstances we are making up here.

If the height is lower than it takes for the objects to approach terminal velocity then they accelerate and impact at the same time.

If they reach respective terminal velocity then the heavier one pushes through the wind resistance better and accelerates longer

If we are talking pure theory and the wind and the atmosphere don't exist - they hit at the same time regardless of mass.

[Big Dave]

Yup.


Was just reading a comment on terminal velocity.

How do you calculate how the rate of acceleration slows as terminal velocity is approached?

[bogan]

Does anybody remember that thing in high school called physics? Perhaps you can help me then.

Does adding weight effect the maximum velocity of a self propelled body in atmosphere?

Imagine it this way. You have two identical cars, side by side on a flat straight piece of road. The cars have identical shapes, identical power, identical everything. Now place a 100kg weight into the boot of one of the cars. Obviously once they set off, the car with no weight in the boot will accelerate faster. But, will this 100kg extra have an effect on the top speed of the weighted car - will it be able to achieve the same top speed?

hmmm, hundy kg weight in the boot and questions about speeding cars. You arent planning to dispose of a body or two are ya?

If we consider the rolling friction to be independant of the cars weight, the qustion becomes, will adding 100kg to the boot of a car affect its aerodynamics? Depending on the car it could, the load on the rear springs will increase, and the load on the front will slightly decrease, changing the angle of the underside of the car relative to the road. It could possibly create a venturi effect furthur sucking the rear down, and create more turbulence at the rear, resulting in a lower pressure and less top speed.

[bogan]

How do you calculate how the rate of acceleration slows as terminal velocity is approached?

i guess itd be f=ma, where downward force=m*9.812 and upwards force is the result of wind friction, so a=net force/mass

[earl]

Well, when you have got this one sorted,perhaps you could answer the question posed by Lindburg when he was crossing the atlantic for the first time. Does a fly, flying in a flying aircraft add to the weight and therefore the fuel consumption?

[ducatilover]

Well, when you have got this one sorted,perhaps you could answer the question posed by Lindburg when he was crossing the atlantic for the first time. Does a fly, flying in a flying aircraft add to the weight and therefore the fuel consumption?

:Punk::love: That is the ultimate question

[Big Dave]

:Punk::love: That is the ultimate question

I would have gone for 'what is the meaning of life, the universe and everything'.

[Metalor]

Well, when you have got this one sorted,perhaps you could answer the question posed by Lindburg when he was crossing the atlantic for the first time. Does a fly, flying in a flying aircraft add to the weight and therefore the fuel consumption?

Yes, because the flys wings are displacing the air in the plane, creating a lifting force on the fly's wings, but the wings are providing a downwards force on the air (pressure down). This downwards pressure would translate to pressure on the floor of the plane. You can imagine this more easily say if a giant bird flew past above the plane, and as it beat is wings down, creating lift for the bird, that pressure from the air would push the plane down.

Haha, it's a pretty clever question though. Ultimately the mass and effect of the fly to the plane is completely negligible.

[Hans]

The engine needs to carry out more work to propel the heavier car at the same speed. All other things being equal, the heavier car will have a lower top speed.

[scracha]

When determinining top speed of a car, the most important one is air resistance (drag). This force is proportional to the square of the velocity so it's numero unu. That's why at very high speeds, you need massive amounts of extra bhp even to gain an extra 1kmph.

Fair is force of air resistance
Cair is the co-efficient of air friction for a given vehicle
v is the vehicles velocity

Fair = -Cair * v^2

There "driving" force in the car is Fgrip (force from the tyres which generally spin from the engine). There's also Fres (force from rolling resistance). Fres is directly proportional to the velocity and in a car. As Fair is "squared" then it takes as the main friction force at roughly above 100Kmph.

F = Fgrip + Fres + Fair

Using Newton's law
a = F / M (accel = force over mass)

You then integrate the accelleration over time but essentially, higher accelleration, a higher top speed.

BUT, larger mass, lower top speed.
BUT BUT BUT
F is also affected by the larger mass as
Fgrip is increased (less slip)
Fres is increased
Fair - well without a wind tunnel, we don't know for sure, but assuming the weight is in the rear of the car we'd assume that Cair is increased as it's nose would be higher.

As Fair is "squared" then I reckon the heavier car would be slower if the weight is put in the boot but faster if the weight was placed further forward. A lot depends on the aerodynamics of the car and also whether we're talking about an 850cc engine or an 8 litre engine. We've also assumed the road is flat.

Fuck..I dunno...my head hurts now.

[MisterD]

The engine needs to carry out more work to propel the heavier car at the same speed. All other things being equal, the heavier car will have a lower top speed.

Newton's first law: in the absence of a net external force a body either remains at rest or moves with constant velocity.

The initial assumptions were that the extra mass of the second car didn't increase the friction / rolling resistance therefore the only two forces to consider are a) the motive force of the engine and b) air resistance. These are equal for both cases therefore the maximum velocity of the cars is the same.

[rickstv]

Oh Bugger this for a laugh, you guys are giving me a headache :bash:

[MattRSK]

v_term=(8ρ(density body) gr)/(3Dρ(density air) )


This is the formula for terminal speed in a fluid (ie. Air), As the density of the body is taken into account I would say the car with the greater mass will have a greater terminal speed.

[Hans]

Only if you drop it from a plane.

[steve_t]

I would have gone for 'what is the meaning of life, the universe and everything'.

42... man, I'm old:shutup:

[bogan]

Only if you drop it from a plane.

What if it was shot from a rail gun, which car would be able to break out of earth orbit easiest, and would it have enough energy to deflect an armageddon comet. I mean, we only have one bruce willis, and we dont wanna use him unless its an emergency :ar15:

[MisterD]

v_term=(8ρ(density body) gr)/(3Dρ(density air) )


This is the formula for terminal speed in a fluid (ie. Air), As the density of the body is taken into account I would say the car with the greater mass will have a greater terminal speed.

I didn't do fluid dynamics as part of my degree...but I'd say that's probably for a sphere falling under influence of gravity...

[MattRSK]

I didn't do fluid dynamics as part of my degree...but I'd say that's probably for a sphere falling under influence of gravity...

Yeah your absolutely right, Just quickly flicked through my notes and thats all I could come up with. Haven't really looked at aerodynamics at all.

[MattRSK]

There are a whole bunch of people who love this sort of question at www.physicsforums.com!

[Metalor]

There are a whole bunch of people who love this sort of question at www.physicsforum.com!

The domain physicsforum.com is for sale. To purchase, call BuyDomains.com at 781-839-7903 or 866-866-2700. Click here for more details.


Well done!

[dipshit]

If the went to the moon and did the same thing we would see the feather and the car reach the ground at the exact same time (provided the were dropped from the same height.)

The Apollo guys did just that...
http://www.youtube.com/watch?v=gtdiHDxh3LU

[MattRSK]

The domain physicsforum.com is for sale. To purchase, call BuyDomains.com at 781-839-7903 or 866-866-2700. Click here for more details.


Well done!

my bad, it has a 's' on the end of forum.

[ducatilover]

I would have gone for 'what is the meaning of life, the universe and everything'.

I think John Cleese has explained all this :yes:

[Big Dave]

I think John Cleese has explained all this :yes:


Douglas Adams.

Which raises the question:

if a tree falls in a forest and it lands on a mime artist - does anybody care?

[Big Dave]

v_term=(8ρ(density body) gr)/(3Dρ(density air) )


This is the formula for terminal speed in a fluid (ie. Air), As the density of the body is taken into account I would say the car with the greater mass will have a greater terminal speed.

As previously posted - it depends on which set of bollox we are addressing.

[ducatilover]

Douglas Adams.

Which raises the question:

if a tree falls in a forest and it lands on a mime artist - does anybody care?

If a honda is in a forest and nobody is around is it still gay?

Nobody really cares about the mime

[imdying]

Does anybody remember that thing in high school called physics? Perhaps you can help me then.

Does adding weight effect the maximum velocity of a self propelled body in atmosphere?

Imagine it this way. You have two identical cars, side by side on a flat straight piece of road. The cars have identical shapes, identical power, identical everything. Now place a 100kg weight into the boot of one of the cars. Obviously once they set off, the car with no weight in the boot will accelerate faster. But, will this 100kg extra have an effect on the top speed of the weighted car - will it be able to achieve the same top speed?
Definitely be lower... more drag on the bearing in the drive line for one.

Easiest way to answer this for yourself, without needing to do any calculations... take it to the extreme. Replace that 100kg with 100000kg... do you think it'll make the same top end? Same applies for the 100kg weight, there's just less difference.

[Metalor]

Gotta be able to apply enough force to overcome the coefficient of friction :P

As long as you can do that It'll accelerate.



But Imdying is right I think. Small bikes with a heavier rider don't have as high top speed as with a smaller rider (maybe it could still get up there but very slowly?) Thing is, engines are not completely efficient, you have loss somewhere along the line so this extra mass could mean more work by the motor and we know some of the energy the engine puts out is heat, so a protion of the top speed must be used in the "creation" of this heat.

Blabbering again, sorry...

[bogan]

Gotta be able to apply enough force to overcome the coefficient of friction :P

As long as you can do that It'll accelerate.



But Imdying is right I think. Small bikes with a heavier rider don't have as high top speed as with a smaller rider (maybe it could still get up there but very slowly?) Thing is, engines are not completely efficient, you have loss somewhere along the line so this extra mass could mean more work by the motor and we know some of the energy the engine puts out is heat, so a protion of the top speed must be used in the "creation" of this heat.

Blabbering again, sorry...

bigger riders weight, or size though?

[scracha]

Only if you drop it from a plane.
Ha, you're spot on there.



The initial assumptions were that the extra mass of the second car didn't increase the friction / rolling resistance therefore the only two forces to consider are a) the motive force of the engine and b) air resistance. These are equal for both cases therefore the maximum velocity of the cars is the same.

Who made these assumptions? Air resistance and rolling friction are always affected by mass. If we pretended they were not then yes, the max velocity would be the same.



www.physicsforums.com!

Fuck. That's me not going to get any work done for a few days now. Oh...there's even a computational physics subforum. Fortran 95 rocks! :gob:



do you think it'll make the same top end? Same applies for the 100kg weight, there's just less difference.

Nope, it affects a number of different forces, not all of which are linear.

[nothingflash]

Douglas Adams.

Which raises the question:

if a tree falls in a forest and it lands on a mime artist - does anybody care?

What if we threw a mime artist and a tree out of a plane......:laugh:

[BMWST?]

But these objects are not being accelerated by gravity alone, so this does not apply in this case.

In this case the energy is being supplied by an engine. I've assumed the energy output of the engines remains constant in both cases (since that was what was said). If the energy output remains the same, then the two vehicles will not accelerate at the same rate.

The heavier car will take slightly longer to reach the same speed.He is asking abot top speed ,not accelleration

[Skyryder]

Big Dave said it best.


So here's another tricky one.


If a tennis ball was the only object in the universe. Can it move??


Skyryder

[p.dath]

Big Dave said it best.


So here's another tricky one.


If a tennis ball was the only object in the universe. Can it move??


Skyryder

Define movement, and the question will be answered.

[Emore]

If a tennis ball was the only object in the universe. Can it move??


No. Movement is only relative when measured against another object.

[Max Preload]

Jesus. It seems there are as many people on here who have no idea of the laws of physics as there are people who don't know how to indicate on roundabouts! I recall a thread a while back regarding CoG as well.

All other things being equal (friction & power) mass does not affect maximum achieveable velocity. It affects acceleration.

[Big Dave]

Jesus. It seems there are as many people on here who

lack social skills. :-P

[slofox]

If a tennis ball was the only object in the universe. Can it move??


Skyryder

Is the universe in itself an object?

[dipshit]

Is the universe in itself an object?


Not necessarily. We say things like 'the known universe'. That is the universe is everything we know of.

If there is no other matter or light or background radiation or gravity... absolutely nothing apart from one tennis ball... then there is nothing else as a reference point to measure its movement against.

[Flip]

Is the universe in itself an object?


Yes but there is still no fixed points of refrence so it's impossible to measure.

[scracha]

All other things being equal (friction & power) mass does not affect maximum achieveable velocity. It affects acceleration.
However, back in the real world, mass does affect friction.

[Marmoot]

The extra weight would create higher friction on the bearings (not the tyre contact patches with ground). But it is still an increased friction.
Friction = mass * friction coefficient.

Because of added friction, the force requirement to maintain equillibrium at higher speed is also higher. Therefore there is less force available to move the car. Ergo, the maximum speed decreases.
It can also be said as if the added friction acts as an additional set of brakes. What happens when you run your car while slightly pressing on the brake? It limits the maximum speed.

On the other hand, if you want to consider the fluid dynamic effects, the lighter car's maximum speed may or may not be limited by the amount of lift caused by the moving air underneath the car. Arguably, the weighted car may or may not benefit from this.
To properly analyse this to a conclusion, you would need a mathematical model on the airflow effect on both cars, and introduce the higher friction into the equation. Only then you would be able to judge whether the effect of added weight is more or less than the effect of lift that limits the lighter car. And only then would you be able to determine which one is faster.

And in regards to the tennis ball, if the universe is larger than the tennis ball then yes it can move relative to the center of the universe. But if the universe in the context is only as big as the tennis ball (e.g., if the universe size is determined by the object contained within) then no the tennis ball would not be able to move due to lack of space.

[MisterD]

So here's another tricky one.


If a tennis ball was the only object in the universe. Can it move??

I'm going to go with yes it can move, but no it can't be moved because there's nothing to apply any force to it...the sound of one hand clapping innit?

[Big Dave]

I'm going to go with yes it can move, but no it can't be moved because there's nothing to apply any force to it...the sound of one hand clapping innit?

Kicking Schrodinger's balls

[bogan]

if the tennis ball is the only thing in the universe, then is it really even a tennis ball, as there is nobeody there to define such a concept.

Also since the universe i generally considered infinite emptyness, no movement could ever be percieved or measured with respect to its confines, meaning any extra weight added to said tennis ball will not affect its top speed of null.

[peasea]

Does adding weight effect the maximum velocity of a self propelled body in atmosphere?


Ask a donut-eating copper in an I-car.

[Big Dave]

http://assets.comics.com/dyn/str_strip/000000000/00000000/0000000/200000/80000/6000/200/286219/286219.full.gif

http://assets.comics.com/dyn/str_strip/000000000/00000000/0000000/200000/80000/6000/200/286220/286220.full.gif

[Skyryder]

I'm going to go with yes it can move, but no it can't be moved because there's nothing to apply any force to it...the sound of one hand clapping innit?


There is no physical force to prevent movement so yes the ball could move but as the tennis ball is the only object in the universe there would need to be an additional object (force as you rightly state) to cause its motion and on this basis the tennis ball could not move as it is the only object. This is the logical answer to the question. But it is not the right one as the question asks can the tennis ball move? Yes it can………No it can not. This is the quandary that the question poses.


Movement, speed, motion etc can only be detected by the position of a secondary object and as such is not part of the answer as the tennis ball is the only object. Herein lies the problem. As there is no way to determine movement does this in itself prohibit movement. Logic would dictate no nor is there any physical barrier to movement.

But movement can only be defined with a secondary object but as there is no secondary object in the question the tennis ball can not be moved as there is no force to move it. But even this analysis of the question is wrong as it assumes that the ball ‘is’ moving and as such needs a secondary object (energy force etc) to create movement. The question makes no statement that the ball is moving or not. It asks can the ball move period.

Like the koan you quoted the question imposes a conceptualization that we can not comprehend and as such is impossible to give a definitive answer one way or the other. But as you no doubt know koan solutions have nothing to do with the problem posed.

But you can get into some strange places trying.


Skyryder

[ready4whatever]

hmm not sure but theory is different from practical. I remember my teacher telling me that if you had a lever long enough you could lift an entire town with your body weight. But try doing it. You wouldnt find a lever that strong, or long, you'd run out of flat land, and so on

[Pixie]

My kitty's breath smells of fish

[cheesemethod]

Thanks for all the educated and not so educated but albeit humorous answers. Has anybody calculated rolling resistance of a motorcycle before? I'm curious to see how much force in that vs drag from the air.