Question

Achargingbullelephantwithamassof5240kgcomesdi- rectly toward you with a speed of 4.55 m/s. You toss a 0.150-kg rubber ball at the elephant with a speed of 7.81 m/s. (a) When the ball bounces back toward you, what is its speed? (b) How do you account for the fact that t

Answer 1

Given:

Mass of elephant = 5240 kg

The initial speed of the elephant = 4.55 m/s

Mass of the rubber ball, m, = 0.15 kg

Inital speed of the rubber ball, v = 7.81 m/s

On substitution in
`V_(2f)` =
`[(2m_(1) )/(m_(1) +m_(2) ) ]V_(1f)` +
`[(m_(2)-m_(1))/(m_(1)+m_(2) ) ] v_(2f)`

`V_(2f)` =
`[\frac{2*5240_{} }{5240_{} +0.15_{} } ](-4.55_{})` +
`[\frac{0.15_{}-5240_{}}{5240_{}+0.15_{} } ] (7.81_{})`

a) The negatıve sign shows that the ball bounces back in the direction opposite to the incident

b) it is clear that the velocity of the ball increases and therefore it is kinetic energy . The ball gains kinetic energy from the elephant.