Question $4(4$ points$)$

$10\frac{m}{s}$

A ball A of mass $1$ kg strikes a block B of mass $6\mathrm{.}9$ kg

resting on a horizontal plane as shown in Figure

below. The ball has a velocity of $10\frac{m}{s}$ to the right

just before striking the block and $5\frac{m}{s}$ to the left just

after the strike. If the coefficient of friction between

the block and the plane is $0\mathrm{.}15,$ determine the

coefficient of restitution between the ball and the

block.