why a ball rebounds after collision with earth?

Answer 1

The ball rebounds because the collision is more elastic but do not consider it as perfectly elastic collision.

Answer 2

Conservation of energy...

Work = energy = (F-W)del x = 1/2 mv^2 = (k del x - mg) del x = 1/2 mv^2; where F = force against the Earth as the ball expands del x from its compressed del x on impact. Note the restitution force (k del x) gives the ball's mass (m) an acceleration of (a); thus, F = k del x = ma, where a is the initial acceleration upward on the rebound.

W = weight of the ball (W = mg) acting against the restitution force (F), m = mass of the ball, v = velocity of the ball as it leaves the Earth on rebound giving it a kinetic energy (KE) = 1/2 mv^2.

So, here's the chain of events that cause the ball to rebound (I'm assuming perfect elasticity). First the ball compresses on impact, creating a force F = k del x; where k = the coeffecitent of restitution and del x is the amount the ball compresses.

Second, the compressed ball decompresses (restitution) and pushes against the Earth with force F acting del x, which gives an energy of F del x = ma (del x) as the ball pushes off Earth. If F = ma > W = mg, then the ball will lift off the Earth because the restitution force is greater than the weight of the ball. Otherwise, the ball will just sit there on the ground...it will not bouce.

As soon as the ball leaves the Earth and is moving upward on the rebound, it has kinetic energy = KE = 1/2 mv^2 because of the net work = F del x - W del x the ball did on decompressing. Therefore KE = net work = m(a - g)del x = 1/2 mv^2; so that, (a - g) del x = 1/2 v^2; and, finally, v^2 = 2(a - g) del x and v = sqrt(2(a - g)del x)

Lessons learned: Mass (m) does not enter into determining the rebound velocity; however, it does enter into determining the acceleration (a). This results from F = k del x = ma; so, that a = (k del x)/m. Also note, if we had assumed less than perfect elasticity, we would have KE < net work because not all the work of k del x would be converted into KE; some of it might become heat for example.

Answer 3

It only rebounds if it's an elastic collision. A ball of snow, for example, doesn't rebound because it's an inelastic collision.


Doug

Answer 4

OK a ball or any other object that hits a wall or any other object harder then it has momentum even when it hits the wall since the wall it harder then it it forces a change of direction if you take a golf ball and throw it through a paper bag the back is not strong enough to take or change the direction so it rips right through untill it hits something harder then it if you take a basket ball and bounce it from chest level at a 45 degree angle it will bounce back at a 45 degree angle these are the laws of physics if it did not bouces back all the energy would have to have been absorbed by something like water like in a swimming pool

a ball of snow absorbes the energy and it spread out ice will bounce pool balls bounce

Answer 5

Because the ball is full of spirit, after having fallen off the horse, it gets up back on it again, it rebounds, it's resilient. We should all be like the ball.