| If 2 balls of rubber and metal are released, then they will hit the ground at the same time, but the metal 1 will hit harder. |
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Asked 2 years ago
by SuperFlyNinjaGuy  United Kingdom |
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7 Points
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"If two balls of the same volume made out of rubber and metal are released from rest, then they will hit the ground at the same time, but the metal ball will hit harder."
This is because metal is heavier, so it will hit harder. But since mass has no dictation of accelerartion or velocity in this case, it will fall the same weather heavy or light.
Am I wrong?
There are a number of terms in the formula for kinetic energy. Only one of them is acceleration--in this example, gravity; another is mass. Therefore the amount of kinetic energy an object has is dependent upon mass. Look up the equation.
That is as close as i can figure to "hitting harder." Meaning, I think, "transferring some amount of kinetic energy/momentum?" Momentum has mass as one term in it's equation too.
The whole "hit harder" part of the question is throwing me off.
The metal ball would (probably) transfer more energy because it would not flex and absorb as much energy as the rubber ball would. But I think the actual force of impact would be the same if the mass were the same.
For instance, if the metal ball and the rubber ball were dropped on a concrete surface, the metal ball would probably chip the surface and not bounce very high. The rubber ball would probably not chip the surface but would bounce a lot higher than the metal ball. I would think the metal ball would have transferred more of its energy directly into the concrete where the rubber ball absorbed a large portion of the energy which then propelled it higher on the bounce. I think the total energy of both drops would be the exact same however.
"But I think the actual force of impact would be the same if the mass were the same."
But the mass isn't the same. The volume is the same. The metal ball would be heavier than the rubber ball, just because metal is heavier than rubber.
It depends of the experiment is conducted in air or a vacuum. Air has a bouyant effect, the less dense rubber ball would therefore feel a greater retarding force than the metal one. So although their acceleration due to gravity is the same, the net acceleration of the metal ball would be greater, giving it greater momentum which would account for it hitting harder.
In a vacuum, assuming the rubber ball is more elastic than the metal one, it will bounce higher so tranfers less energy to the surface. Also, if the rubber ball deforms on impact, I think it will transfer that energy a tiny bit slower, it's essentially cushioned.
What is "hit harder"? More force, more kinetic energy, more energy transfer?
Does a train hitting you while moving at 1 mph "hit harder" than a car at 60 mph? This could be argued in the context of "hits harder" either way. The train has far more kinetic energy due to its mass. But because of its slow speed you are just pushed out of the way, where as the car will kill you.
What is the mass of each ball? Are they the same? Assuming they are equal mass, they will have equal kinetic energy. The steel ball is going to transfer more of its energy to the object it hits. Whereas the ball is going to expend more (by percentage) of its energy in deforming itself, there for leaving less to transfer to what it hits.