Nother physics question

[LBD]

seeing we liked the last one so much, heres another...

You have an accurate scale and a 10L container of water. At sea level this weighs (has a mass of) 10 kg precisely, and the scale reads 10kg.

You then climb a very high mountain with scale and water record the reading.

You then journey down a very deep mine shaft and take another recording.

Multi Choice, do the readings ON THE SCALES show...
a) Heavier both up the mountain and down the mine shaft
b) Lighter both up the mountain and down the mine shaft
c) Heavier up the mountain and lighter down the mine shaft
d) Lighter up the mountain and heavier down the mine shaft

I will give it a couple of days then if the correct answer is not posted with the explaination I will....

[gatch]

Is this a trick ?

Wouldn't the mass stay the same..

[bogan]

im going to go with d) as i reckon the pressure head from the atmosphere will have a larger affect than the change in gravity at different altitudes.

[bogan]

Is this a trick ?

Wouldn't the mass stay the same..

the mass will, but the scales will read the weight different i reckon

[Big Dave]

Deefer for David

[LBD]

Is this a trick ?

Wouldn't the mass stay the same..
No its not a trick question, yes the mass would stay the same, the scales change...have clarified in the question



the mass will, but the scales will read the weight different i reckon

yep its as simple as the question now reads.

There is a simple logical factual answer...

[Jantar]

Very simple. The scales will show a lighter weight at both locations. (answer b).

If the mountain could be as high as 35,700 km (at the equator) then the water would be weightless. Similarly if the mine shaft went right to the center of the earth then it would again be weightless.

[Hans]

Nope. Gravitational field of the Earth diminishes with distance. However, the higher and therefore more massive the mountain, the more you'd have to factor in the gravitational force of the mountain itself. As for the mine shaft, I'm guessing the deeper you went the more the gravitational force would change direction, rather than intensity. Sum of intensities of different directions shouldn't change much. I'd rather noone quoted me on any of this, it's half past midnight.

[Jantar]

Nope. ......
Yep. It was one of the first discussions we had in year 1 physics back in 1971.

First; the mountain: Because it is a mountain it is steep, and the circumference of the base can never be greater than the circumference of the earth. The center of mass of the entire system cannot be more than 1/8 (volume of a cone) of the distance from the present center of the earth to the top of the mountain, so the water is significantly further away from the center of mass and the gravitional effect is reduced.

In the mineshaft there is mass above which is pulling upwards, and at the center of the earth all gravitational effects are balanced.

[TOTO]

I go for answer D.

If the earth centre core is a magnet, up high at the mountain , it is further from the magnet, thereofre less gravitational pull, and down the shaft it is closer to the magnet, hence scale will read a heavier weight.

did I win the $100 000 or I have to go get married in the nude ?

[Jantar]

I go for answer D.

If the earth centre core is a magnet, up high at the mountain , it is further from the magnet, thereofre less gravitational pull, and down the shaft it is closer to the magnet, hence scale will read a heavier weight.

did I win the 100 000 or I have to go get married in the nude ?
Where do I get this water that is attracted to a magnet? :bleh:

[TOTO]

Where do I get this water that is attracted to a magnet? :bleh:

tap water will do.

[Big Dave]

Where do I get this water that is attracted to a magnet? :bleh:

Lake Macquaire - Just near the smelter and cooling outlet for the Power Station.

[Hans]

Yep. It was one of the first discussions we had in year 1 physics back in 1971.

First; the mountain: Because it is a mountain it is steep, and the circumference of the base can never be greater than the circumference of the earth. The center of mass of the entire system cannot be more than 1/8 (volume of a cone) of the distance from the present center of the earth to the top of the mountain, so the water is significantly further away from the center of mass and the gravitional effect is reduced.

In the mineshaft there is mass above which is pulling upwards, and at the center of the earth all gravitational effects are balanced.

Fail. In the mineshaft gravity will also act sideways, not just up or down. Also thread/question fail IMHO. please set some proper paramaters for the question. Ie. what to regard/disregard, how high, how deep etc. Let's not do kindy-physics. Some considerations change the outcome.

[Jantar]

Fail. In the mineshaft gravity will also act sideways, not just up or down. Also thread/question fail IMHO. please set some proper paramaters for the question. Ie. what to regard/disregard, how high, how deep etc. Let's not do kindy-physics. Some considerations change the outcome.
Oh dear. Draw the vector diagram. Exact values are not required because on the surface of the earth there is no upwards attraction vector. Yes there are some almost sidewards ones that cancel each other out. As you get deeper the integral of all vectors reduces as the strength of the upwards increases. Again all sidewards cancel out.

[TOTO]

Oh dear. Draw the vector diagram. Exact values are not required because on the surface of the earth there is no upwards attraction vector. Yes there are some almost sidewards ones that cancel each other out. As you get deeper the integral of all vectors reduces as the strength of the upwards increases. Again all sidewards cancel out.

where can I download the subtitles for this movie ?

[LBD]

I go for answer D.

If the earth centre core is a magnet, up high at the mountain , it is further from the magnet, thereofre less gravitational pull, and down the shaft it is closer to the magnet, hence scale will read a heavier weight.

did I win the $100 000 or I have to go get married in the nude ?

When do the wedding invites go out and do I get one?


Fail. In the mineshaft gravity will also act sideways, not just up or down. Also thread/question fail IMHO. please set some proper paramaters for the question. Ie. what to regard/disregard, how high, how deep etc. Let's not do kindy-physics. Some considerations change the outcome.

No considerations change the out come any consequence....The answer is simple and logical. ..

Kindy physics....like the concept, lets see who can think clearly on a cloudy day... and graduate from kindy as you put it.

[YellowDog]

Isn't this related to that Archemidies fellow and his 'upthrust' pv constant?

1971 sounds about right.

[Usarka]

What if the mineshaft was sooo deep that you ended up weighing the water exactly in the center of the earth.....?

[Fatt Max]

Erm, sorry having trouble with this....

Got the first bit, no problems, but I am having trouble getting up the mountain....you see there is an elephant in the way...erm.....

[davebullet]

e) both heavier and lighter. Heavier once I've drunken the 10L of water, then lighter as I stop riding to get petrol and go for a pee.

[rainman]

What if the mineshaft was sooo deep that you ended up weighing the water exactly in the center of the earth.....?

Well, then it'd be steam... but so would you, so the answer is irrelevant!

[Usarka]

If you climbed the mountain the lower air pressure would cause the water to expand, leaking out of your exactly 10l container.

[Bass]

Oh dear. Draw the vector diagram. Exact values are not required because on the surface of the earth there is no upwards attraction vector. Yes there are some almost sidewards ones that cancel each other out. As you get deeper the integral of all vectors reduces as the strength of the upwards increases. Again all sidewards cancel out.

Exactly right

[MisterD]

If you climbed the mountain the lower air pressure would cause the water to expand, leaking out of your exactly 10l container.

The lateral thinking prize goes to...:clap:

Jantar has the correct answer, as long as we're assuming uniform density for the earth and the mountain. In reality the core of the Earth is more dense than the crust so depending on the way the density varies with depth the weight could increase or decrease.

Gravitational anomalies are one of the main methods of "looking" at the structure of rocks under our feet...I spent a memorable few months hooning around Northumbria trying to work out the size of an area of granite back in the day. Ok mainly memorable because of the pubs and the fact that a 1.6L Cavalier estate will get airborne...

[TOTO]

When do the wedding invites go out and do I get one?


NZ_CBR has the ivites to the wedding ... (http://www.kiwibiker.co.nz/forums/showthread.php?t=106927)

[bogan]

a question about these scales. Do they operate with the old spring way, or a fandangled sealed pressure transducery setup. For example when the air pressure is greater or lesser do they add that to thereading? I assumed they did, but now im not so sure.

[Metalor]

Yep. It was one of the first discussions we had in year 1 physics back in 1971.

First; the mountain: Because it is a mountain it is steep, and the circumference of the base can never be greater than the circumference of the earth. The center of mass of the entire system cannot be more than 1/8 (volume of a cone) of the distance from the present center of the earth to the top of the mountain, so the water is significantly further away from the center of mass and the gravitional effect is reduced.

In the mineshaft there is mass above which is pulling upwards, and at the center of the earth all gravitational effects are balanced.

You have to get VERY far away from the earth for a noticable change in earths gravity (think GPS satellites running in fast time due to reduced gravity).

No mountain, for 'all intended purposes' is going to EVER be large enough. Unless you have an EXTREMELY precise scale... fucken nanokilo shit there motherfucker!

[Marmoot]

Don't forget that up the high mountain and down the deep mineshaft would have an effect on temperature. Temperature affects the weight.

So to determine whether the weight measured by the scale would be lighter or heavier, you need to first construct a mathematical model that incorporates the temperature effect as well as the gravity effect. Only after that would you be able to determine the total effect gained at each location and determine the correct answer.

Without knowing the actual height/depth of the place (in above-sea-level terms), I don't think you can form a conclusive answer.

[Big Dave]

It's still D.

It would be lighter at the top of the mountain because you'd spill some climbing it and also need a drink.

It would be heavier in the mine shaft because of the gold.

[R6_kid]

Don't forget that up the high mountain and down the deep mineshaft would have an effect on temperature. Temperature affects the weight.

Temperature affects the volume, not the weight. It becomes more dense at colder temp, less dense at higher temp, but the weight remains the same until such time as some of the water starts evaporating.

[Winston001]

Very simple. The scales will show a lighter weight at both locations. (answer b).

If the mountain could be as high as 35,700 km (at the equator) then the water would be weightless. Similarly if the mine shaft went right to the center of the earth then it would again be weightless.

10+ characters :niceone:

[_STAIN_]

none of the above, the mass will not change

[p.dath]

That's a toughy

First a few assumptions. The scales will display the correct weight at all altitudes.
Secondly the weight is measured relatively to the surface of the earth.

As you go up gravity will reduce, and so will weight.

As you go down towards the centre of the earth, away from the surface, and assuming you don't go past the centre of the earth, I would expect the weight to reduce. This is because gravity should reduce as the body of earth increases above you (and hence the gravity pulling you towards the surface should increase, until you reach the centre of the earth where the gravitational field will be balanced out).

So my guess is (b).

[Marmoot]

Temperature affects the volume, not the weight. It becomes more dense at colder temp, less dense at higher temp, but the weight remains the same until such time as some of the water starts evaporating.

Sorry, need to clarify.

Temperature does not affect mass.
But temperature affect the equipment measuring the mass (spring rate of the scale, internal friction within the scale mechanisms, etc).
Unless you have an ideal scale. But there is no such thing as ideal scale, and the problem did not stipulate this.

I would prefer the added weight in the deep mine due to the gold, though.
Obviously, you're an entrepreneur and I'm a researcher. Unfortunately this means given the same amount of work, you'll be richer.

[Warr]

That's a toughy

......... you don't go past the centre of the earth, I would expect the weight to reduce. This is because gravity should reduce as the body of earth increases above you (and hence the gravity pulling you towards the surface should increase, until you reach the centre of the earth where the gravitational field will be balanced out)....
Where do you think gravity is coming from... the earths surface or the centre of the earth ?

I as un uneducated guesser go with (d) at this point :)

[R6_kid]

Where do you think gravity is coming from... the earths surface or the centre of the earth ?

The Moon... DUH!!!

[MattRSK]

Where do you think gravity is coming from... the earths surface or the centre of the earth ?


Gravitons.

[p.dath]

Where do you think gravity is coming from... the earths surface or the centre of the earth ?

I as un uneducated guesser go with (d) at this point :)

Gravity comes from everything with mass. You have a gravitational field - it's just very small.

Initially at the earth's surface all of the earth's mass is below you, so the only gravitational field that exists is pulling you down.

As you go below the earth's surface some of the earth's mass is now "above" your head. So now there is a gravitational mass "below" you pulling you down, and a mass above your head pulling you up.
The net effect is that as you travel towards the earth's centre gravity should steadily reduce to zero.
At the earth's centre you have half the earth below you and half above you. They both exert an equal but office force on you, which cancel each other out.

That's my thoughts.

[Big Dave]

none of the above, the mass will not change

This is not a mass debate.

[MisterD]

You have to get VERY far away from the earth for a noticable change in earths gravity (think GPS satellites running in fast time due to reduced gravity).

No mountain, for 'all intended purposes' is going to EVER be large enough. Unless you have an EXTREMELY precise scale... fucken nanokilo shit there motherfucker!

Er, in fact no, we learnt to use the equipment by taking measurements on every floor of the Physics building in Newcastle.

http://farm1.static.flickr.com/215/489737221_a30f0c0026.jpg

[Big Dave]

Er, in fact no, we learnt to use the equipment by taking measurements on every floor of the Physics building in Newcastle.



The Shearer Scale. Belta.

[LBD]

Its a perfect set of scales...reads constant irrespective of temp or alt or atmospheric pressure.

Its not a complicated question...its relatively simple and logical.

To dispell drink or evaporation...the 10 kg mass of water could be 10 kg of gold or pebbles from birdlings flat or used traffic infringment notice books from the Police archives....

[MisterD]

The Shearer Scale. Belta.

Would've been the Keegan scale in them days BD...

[bogan]

Its a perfect set of scales...reads constant irrespective of temp or alt or atmospheric pressure.

Its not a complicated question...its relatively simple and logical.

To dispell drink or evaporation...the 10 kg mass of water could be 10 kg of gold or pebbles from birdlings flat or used traffic infringment notice books from the Police archives....

ahh, in that case, we must take into account the density of the mass and its bouyancy at different air pressures/ different altitudes, it may even weigh the most on the mountain because of this

[EJK]

The answer is B) because I drank some on the way up Mt Everest because I was thirsty, and I spilt some when going down the mine shaft.

[Big Dave]

Would've been the Keegan scale in them days BD...

Robson - it doesn't matter - the longer the season the longer the faces.

The Toon Scale.

[Metalor]

Don't forget that up the high mountain and down the deep mineshaft would have an effect on temperature. Temperature affects the weight.

So to determine whether the weight measured by the scale would be lighter or heavier, you need to first construct a mathematical model that incorporates the temperature effect as well as the gravity effect. Only after that would you be able to determine the total effect gained at each location and determine the correct answer.

Without knowing the actual height/depth of the place (in above-sea-level terms), I don't think you can form a conclusive answer.

Mate, it would affect the DENSITY.. .not the mass. The amount of water you had wouldn't change but it's VOLUME would.

[avgas]

Lighter - if you walk up a moutain your going to drink the water.

[bogan]

wikipedia tells us some shit


Gravity decreases with altitude, since greater altitude means greater distance from the Earth's centre. All other things being equal, an increase in altitude from sea level to the top of Mount Everest (8,850 metres) causes a weight decrease of about 0.28%. (An additional factor affecting apparent weight is the decrease in air density at altitude, which lessens an object's buoyancy.[3]) It is a common misconception that astronauts in orbit are weightless because they have flown high enough to "escape" the Earth's gravity. In fact, at an altitude of 400 kilometres (250 miles), equivalent to a typical orbit of the Space Shuttle, gravity is still nearly 90% as strong as at the Earth's surface, and weightlessness actually occurs because orbiting objects are in free-fall.

If the Earth were of perfectly uniform composition, during a descent to the centre of the Earth, gravity would decrease linearly with distance, reaching zero at the centre. In reality, the gravitational field peaks within the Earth at the core-mantle boundary where it has a value of 10.7 m/s², because of the marked increase in density at that boundary.[citation needed]

so theres at least three things in play, centripetal acceleration, gravitational accelleration, and bouyancy/density force

[Metalor]

It would be lighter at the top of the mountain because you'd spill some climbing it and also need a drink.

It would be heavier in the mine shaft because of the gold.

Best answer.

[LBD]

And if the mass was in the form of a piano n yer dropped it down a working mine shaft, then at the bottom you would have ....A Flat Minor....:doh:

[Big Dave]

Would've been the Keegan scale in them days BD...

Or - It quit mid season????

[Winston001]

This is not a mass debate.

Oh sorry, just the 5 minute argument then......?:eek:

[Big Dave]

....A Flat Minor....:doh:

I thought Gravity was the key.

[Winston001]

Gravitons.

Mmmmmm.........NOPE.

Actually we don't really know where gravity comes from. Einstein would say its an effect of space bending. But that's not exactly helpful.

I prefer to see it as tiny pixies tugging on stuff when you try to lift it. As you walk up the mountain, it gets colder and only the Sherpa pixies hang about, so the bucket gets lighter.

Going underground requires Dwarf pixies who are a grumpy lot so the woodland pixies leave them to it. The bucket once again gets lighter.

[Gareth123]

WOOOOSSSSSH

This whole thread flew straight over my head. I read all the pages trying to understand and make my intelligence stretch just a little bit further. And stretch it did. Then it snapped back and I just have a headache.

If the conatiner was filled with beer you wouldn't even get a chance to weigh it, some plonker would come along and drink it.

[bogan]

seeing we liked the last one so much, heres another...

You have an accurate scale and a 10L container of water. At sea level this weighs (has a mass of) 10 kg precisely, and the scale reads 10kg.

You then climb a very high mountain with scale and water record the reading.

You then journey down a very deep mine shaft and take another recording.

Multi Choice, do the readings ON THE SCALES show...
a) Heavier both up the mountain and down the mine shaft
b) Lighter both up the mountain and down the mine shaft
c) Heavier up the mountain and lighter down the mine shaft
d) Lighter up the mountain and heavier down the mine shaft

I will give it a couple of days then if the correct answer is not posted with the explaination I will....

did some little bit huckery calculations (lots of bored waiting for windows 7 to instal) and looks to be B)Lighter both ways, regardless of mountain hieght of mine shaft size. Taking into account Displaced air bouyancy, gravity changes, and centripetal accleration.

[ready4whatever]

Answer me this

If you fire a bullet into the sky at 900 m/s ,how fast will it be going when it comes down and hits you in the face?

[Big Dave]

Answer me this

If you fire a bullet into the sky at 900 m/s ,how fast will it be going when it comes down and hits you in the face?


http://www.grc.nasa.gov/WWW/K-12/airplane/Images/termv.gif

[LBD]

So the aim, was pose a straight forward logic thinking gravity question…

Gravity is an attractive force one mass exerts on another mass.

We all know that the further from the surface of the earth we move the portable mass, the less the scales will read until we go beyond any of the earths discernable gravitational force.

For normal thinking, the force of gravity is calculated from the center of the mass, but what happens when you lower one mass inside the other? The further toward the center of the large mass (Earth) the more of the earth's mass is above the 10kg . This mass above, also exerts a gravitational pull on the 10 kg, countering the pull toward the centre of the earths mass….The deeper the mine the less weight detected by the scales.

Correct answer was B

Blings to those on the ball….

Jantar was the first….His turn…..

[Ronin]

You are all missing the point. In todays society we should be asking:



How does the water feel about being the centre of an experiment.
Did the water receive enough hugs as a rain drop
Are there any possible treaty claims that could arise from this experiment
Is the water speeding when you take it down the shaft?

[Big Dave]

Is the water speeding when you take it down the shaft?



Beavis voice: he said 'shaft'. hsssshsss

[MisterD]

Correct answer was B

Blings to those on the ball….

Jantar was the first….His turn…..

My further reading indicates that in reality because of the density changes within the Earth, gravity increases and peaks at the mantle/core boundary...

[Big Dave]

My further reading indicates that in reality because of the density changes within the Earth, gravity increases and peaks at the mantle/core boundary...

I just dug a hole down to it in the back yard and can verify that.

[Usarka]

is this busted yet?

[bogan]

For normal thinking, the force of gravity is calculated from the center of the mass, but what happens when you lower one mass inside the other? The further toward the center of the large mass (Earth) the more of the earth's mass is above the 10kg . This mass above, also exerts a gravitational pull on the 10 kg, countering the pull toward the centre of the earths mass….The deeper the mine the less weight detected by the scales.

Correct answer was B


right answer, wrong working imo


My further reading indicates that in reality because of the density changes within the Earth, gravity increases and peaks at the mantle/core boundary...

agreed, as the mass is moved down the mineshaft, it has a larger gravitational force, but.... the air becomes denser, so the weight of the displaced mass of air greatly increases, making the water bouyant, and lighter than it was at the earth surface.

[LBD]

I just dug a hole down to it in the back yard and can verify that.

Unpredicted Volcano erupts in residential back yard...hundreds die trapped in lava flows......City evacuated

[MisterD]

Unpredicted Volcano erupts in residential back yard...hundreds die trapped in lava flows......City evacuated

At least we'll have a good photographer in the right place to record the excitement...