Do heavier objects fall faster?

oddjob62 said:
Huh? if i drop a cat from my window it will "slow down"? Surely the moment i release it, it's velocity is zero... does that mean cats can hover? I always knew they were strange creatures :p
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It's accelaration will drop to zero at it's terminal velocity. It's actual velocity will increase to a maximum (if it has enought time to do so)
 
xsnv said:
It's accelaration will drop to zero at it's terminal velocity
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Ahh but you said slow down, which is change in velocity not change in acceleration ;)

That's the same with any object... not just cats.
 
As said both object will land at the same time. There is footage from the moon landings showing an astronought performing this experiment as there is no atmosphere on the moon.

Also, it doesn't matter where you do this experiment as proven by the moon experiment. The only difference between any two gravitational bodies is how fast the objects fall, but in all cases, ignoring air resistance, both objects land together.
 
Abyss said:
In this case, think about if a ball was dropped from a height of 1m, the ball would move almost the entire metre, and the earth would barely move. This is due to Newtons law wherby the greater the mass an object has, the greater its gravitational pull.
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No it isn't. By Newton's 3rd law, there is an equal and opposite force between the two objects. The reason the earth hardly moves is because although the forces may be equal, the mass of the earth is much much larger. It takes a *lot* of force to move the earth significantly!
 
haha we literally just been doing that an university in engineering mechanics :p

F=ma. the acceleration due to mavity is constant at 9.81 (assuming no air resistance or wind and terminal velocity isnt reached etc). Its just the more mass an object has the more umph it has when it hits you. The more mass an object has (basically the heavier it is) the faster the top speed will be as it falls due to a higher terminal vel.
 
if there's no resistance there is no terminal velocity just an impact velocity.

Objects only have a terminal velocity when the ma is equal to the resistance

resistance in atmosphere increases with the square of speed. ;)

Thats the reason the feather and hammer hit the moon at the same time they are accelerating at the same rate in ms^2. (whatever the mavity of the moon is)
 
proof:

acceleration is a constant 9.8ms^-2 due to mavity.


using an equation of motion:
v=u + at

v=final velocity
u=initial velocity
a=acceleration
t=time

Mass does not feature in this formula, therefore it has no effect.


eg:
If you shoot a gun horizontally, and drop a bullet from the same height. They will hit the floor at the same time.
 
Why is everyone a) simplifying and b) getting it wrong?

As was mentioned earlier, the gravitational force between two objects is:

GMm
----- = F = ma
r^2

This means two things. 1) It's dependant on both the masses of the objects. Yes, the force on earth between a pea and a cannonball is different. However, if you want the acceleration of the pea (for example), you'll find that the mass of the pea divides through, so the acelleration is dependant only on the mass of the earth, and the distance from the earth. Therefore, ignoring air resistance and assuming dropped at the same height, the pea and the cannonball will accelerate at the same rate. 2) It's dependant on the distance they're apart. However, this is distance between the centers of mass of the objects, and relative to the radius of the earth, you're not going to get a very big percentage difference, even if it is squared, so we can ignore that bit.

On the moon, the acceleration of the object being dropped (pea, whatever) will be different, because the mass of the object it's being attracted towards (moon this time) is different to what it was before (earth). mavity is weaker on the moon, things fall slower there, because the moon is less massive than the earth. A cannonball and a pea on the moon will still hit the moon's surface at the same time, but that time is different to the time it would take on the earth given the same height. You can see this on the youtube video shown earlier.

How is this hard?
 
Had a similar argument this morning!

Would a heavier car accelerate faster down a hill than a lighter car?

This was a 1.4 Polo vs 1.4 Golf argument (The Golf being heavier and thus normally slower, but I absolutely burned my mate completely which doesn't usually happen)
 
xsnv said:
curvature of space-time not just space. It seems easy to get your head round because of the analogy of a heavy ball on a piece of cloth. now imagine a 3D cloth ie all around the ball. How does it curve ;)
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I didn't say "space-time" as I thought it sounded a little pedantic for this forum. No, I still find it fairly easy to imagine :)
 
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Blinkz said:
Right having a great Saturday night discussion with my house mates. Basically we are talking about mavity. We are assuming no friction, air resistance etc

I think that objects will fall towards each other at the same rate. My thoughts on this is that as the mass of an object increases the gravitational force increases, however the increase in mass also increases the force needed for the same acceleration, using F=ma

However my mate says this is wrong and that heavy objects fall faster. His example of this is the earth and the moon. The acceleration towards the earth is bigger then the acceleration on the moon.....

any thought??
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No air & friction resistance: A feather would fall at the same speed as a bowlingball for example.

With resistance &friction: lighter, bigger objects will fall faster as smaller/heavier objects...
 
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The applied force from the earth upon the object is purely dependant on the mass of that object. As such, force is proportional to mass and acceleration is that constant. Therefore they will both fall at the same speed.
 
They fall at the same velocity, as NASA helpfully demonstrate here

EDIT: That'll teach me to read the entire thread next time, clip has already been posted
 
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georges said:
v=u + at

v=final velocity
u=initial velocity
a=acceleration
t=time
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Awww, i was goint to use that Formula.

Also, if you use s = ut + 1/2at^2 you'll find that the times will be the same.
 
Linoge said:
Go to the top room in your house, get a feather and an apple and drop them both out of your window and report back the results. I think you'll be surprised. :p
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That wont work, because a feather although lighter has larger surface to area along with gaps so it FLOATS.
 
Blinkz said:
Right having a great Saturday night discussion with my house mates. Basically we are talking about mavity. We are assuming no friction, air resistance etc

I think that objects will fall towards each other at the same rate. My thoughts on this is that as the mass of an object increases the gravitational force increases, however the increase in mass also increases the force needed for the same acceleration, using F=ma

However my mate says this is wrong and that heavy objects fall faster. His example of this is the earth and the moon. The acceleration towards the earth is bigger then the acceleration on the moon.....

any thought??
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Did you go to school or what? :confused:

Its basic Physics tought at primary school.

Well having said that the standard of science teaching these days it doesnt surprise me.
 
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