Physics question

[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

[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

[Big Dave]

I think John Cleese has explained all this

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!

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.