a) Let v1 and v2 be the velocities of the two balls after the collision. According to the law of conservation of momentum,
mv0 = mv1 + mv2
v2 = v1 + 2ev0
e < 1
b)
Using the law of conservation of momentum,
p = p1 + p2
When the angle between the p1 and p2 is 90o, p > p1 + p2