Exercise 1: Suppose that two balls collide but that we have attached a perfect l

Question

Exercise 1: Suppose that two balls collide but that we have attached a perfect little spring to one of them. It compresses as they collide and the balls do not deform in any appreciable way. Could we think of this as a perfectly elastic collision?

Exercise 2: Suppose that two balls collide and the entire process is one dimensional. There are no forces from agents external to the system. Ball 1 has a mass of 1kg and an initial velocity of +9m/s. Ball 2 has a mass of 4kg and an initial velocity of 1m/s. After the collision, ball 1 has a velocity of 7m/s and ball 2 has a velocity of +3m/s. Was momentum conserved in this collision?

Exercise 3: Referring to exercise 2, if there was no change in any sort of potential energy, was the total work done by the internal forces zero or different from zero?

Explanation / Answer

(1) Elastic collision is defined as the collision where momentum and energy remain conserved.
So here the kinetic energy of the ball will get converted into the potential energy of the spring.
so we can say this is an example of elastic collision.
(2)m1 = 1 kg V1 = 9 m/s
m2 = 4 kg V2 = 1 m/s
initial momentum = m1V1 + m2V2 = (1*9) +(4*1)= 13 kgm/s
Final
m1 = 1 kg V1f = 7 m/s
V2f = 3 m/s
final momentum = (1*7) +(4*3) = 19 kgm/s
therfore the initial and final momentum are different so momentum is not conserved.
(3)Zero

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