Physics question about balls

[Bushmaster]

I have three balls.

A steel ball bearing, a ping-pong ball and one of those bouncy hard rubber balls.

All the same size.

I drop them all from the same height, onto a smooth marble floor.

Q1: Which one will hit the ground first?

Q2: Which one will bounce the heighest?

Q3: Which one will keep bouncing the longest?


Dunno about 1 & 2, but it is a foregone conclusion that the ping-pong ball will bounce the longest and bounce under the table, sofa, chair and finally end up behind the TV, while the other two behave themselves.

But why?

[Mc Lovin]

i dont know about you but the last thing i would want to do with my balls is drop them on a hard marble floor

Edited by Mc Lovin on Friday 19th September 17:07

[timbob]

They should all hit the ground at exactly the same time.

I assume the rubber ball will bounce highest, but I'm not sure about longest.

[Hereward]

Just don't worry about it, man.

[bobt]

Bushmaster said:

I have three balls.

A steel ball bearing, a ping-pong ball and one of those bouncy hard rubber balls.

All the same size.

I drop them all from the same height, onto a smooth marble floor.

Q1: Which one will hit the ground first? all the same time (in theory)

Q2: Which one will bounce the heighest? the rubber one probably

Q3: Which one will keep bouncing the longest? the rubber one definitely

[scorp]

timbob said:

They should all hit the ground at exactly the same time.

They would in a vacuum but i guess drag will affect the pingpong balls descent.

[cqueen]

They'll all hit at the sane time. The ball bearing with bounce highest amd longest.

[Bushmaster]

Drop height say 1.5 metres.

I would say the steel ball hits last as it has more inertia, so slower to speed up.

With greater height the steel ball should overtake the pp ball as air resistance comes into play.

[_Deano]

i thought that all balls, no matter what they are made of (or was that from any height); will bounce around 8 to 10 times before loosing the energy to break from gravity.
I can remember something from my maths days in school. Actully i can only really remember it as a friend and I were throwing a rubber ball as hard as we could to make a difference and one of the flubber like balls hit the floor and shot off at an angle to only smacked a girl in the side of the head.
pi$$ed ourselves with laughter, even now.

Edited by _Deano on Friday 19th September 17:21

[Bushmaster]

But surely the ping pong ball and rubber ball will deform more than the steel ball, so the steel ball will retain more energy for longer?

But why does the ping pong ball seem bouncier?

[ThatPhilBrettGuy]

cqueen said:

They'll all hit at the sane time. The ball bearing with bounce highest amd longest.

Correct, assuming a perfect non energy absorbing floor.

[V8mate]

_Deano said:

i thought that all balls, no matter what they are made of (or was that from any height); will bounce around 8 to 10 times before loosing the energy to break from gravity.
I can remember something from my maths days in school. Actully i can only really remember it as a friend and I were throwing a rubber ball as hard as we could to make a difference and one of the flubber like balls hit the floor and shot off at an angle to only smacked a girl in the side of the head.
pi$$ed ourselves with laughter, even now.

Edited by _Deano on Friday 19th September 17:21

Concrete ball v rubber ball - will both bounce 8-10 times?

[crackthatoff]

you'd have to take into account the airspeed velocity and indeed whether the swallow carrying it is fully laiden and african?

[s2art]

need the coefficient of restitution of the various balls to answer this.

[kambites]

The "all objects fall at the same speed" rule is only true in a vacuum. Assuming they all have the same surface smoothness, the densest will hit the ground first (presumably the ball bearing) for two reasons.

1) The ratio of its density to that of the air is greatest
2) The ratio of its mass to its aerodynamic drag is greatest

Instead of air, think about dropping them in water... the bearing is probably the only one that will hit the ground in that situation...

Which will bounce highest and for longest is more complicated and depends on all sorts of things about both the balls and the floor. If the floor is perfectly hard, the bearing will probably bounce highest because it has least damping effect (few common things are closer to being perfectly elastic than steel, hence its use in springs). If there is any give in the floor, the rubber one will probably bounce highest and longest.

[Frederick]

Bushmaster said:

I have three balls.

:childishroffle:

[NobleGuy]

scorp said:

timbob said:

They should all hit the ground at exactly the same time.

They would in a vacuum but i guess drag will affect the pingpong balls descent.

[Spiritual_Beggar]

Q1 is the steel ball. on earth gravity plays a part, and the steel balls mass will make it fall faster. in a vacuum they all hit at sametime.

Q2 the bouncy ball

Q3 the bouncy ball

[outlaw biker]

Bushmaster said:

I have three balls.

A steel ball bearing, a ping-pong ball and one of those bouncy hard rubber balls.

All the same size.

I drop them all from the same height, onto a smooth marble floor.

Q1: Which one will hit the ground first?

Q2: Which one will bounce the heighest?

Q3: Which one will keep bouncing the longest?


Dunno about 1 & 2, but it is a foregone conclusion that the ping-pong ball will bounce the longest and bounce under the table, sofa, chair and finally end up behind the TV, while the other two behave themselves.

But why?

Depends on how high you dropped they from. Surface area and friction are going to play a part. But I'd guess the ping pong ball would hit last.

I guess the rubber ball would bounce both the highest and longest.

[Pigeon]

ThatPhilBrettGuy said:

cqueen said:

They'll all hit at the sane time. The ball bearing with bounce highest amd longest.

Correct, assuming a perfect non energy absorbing floor.

...I guess a "smooth marble floor" can be taken as the OP's attempt to specify a perfect non-energy-absorbing floor... so that's a reasonable assumption. We don't seem to have a reason to assume a vacuum though...

In a vacuum they'd all hit at the same time... in air the steel ball will hit first, then the rubber one, then the ping-pong ball.

On a perfect floor the steel ball will bounce highest - it is reasonable, I think, to assume that it has a higher coefficient of restitution than a rubber or plastic ball - moreover, in air, it will be the one that's lost the least proportion of its energy to drag when it hits.

For the same reasons the steel ball will keep bouncing the longest.

On a real floor it gets more complicated as very few surfaces are a sufficiently close approximation to a perfect non-energy-absorbing floor to allow the steel ball to "show its full potential". You can do pretty well though by dropping a steel ball onto glass from a height of a centimetre or less, it'll bounce hundreds of times and you'll hear the rising note as they get closer and closer together.