An angry rhino with a mass of 2700 kg charges directly toward you with a speed of 4.70 m/s. Before the events, you throw a 0.180-kg rubber ball directly at the rhino with a speed of 6.56 m/s.

Question

Determine the speed of the ball after it bounces back elastically toward you.

=?

Answer 1

If you assume that the rhino is infinitely mor = e massive than the rubber ball (also the rhino is pushing off of the earth, so conservation of momentum doesn't really apply - it won't slow down) and you assume the ball is completely elastic, it will bounce back with the same speed + the 2 times the speed of the rhino..

The full equation for elastic collision is

v₁' = (m - M)/(m+M) * v₁ + (2M)/(m+M) * v₂

As M>>m

v₁' = -v₁ - 2v₂ as I stated earlier.