Question

As shown, tennis ball A rolls off the top of a 10.0 m high wall, falls 4.00 m, and strikes another tennis ball, B, obliquely. (Figure 1) Before the collision, tennis ball Bhas a speed of 19.0 m/s as it moves upward. Each ball's mass is 57.0 g and the collision's coefficient of restitution is 0.630.(Figure 2) In the figure, ?1=30.0? and?1=20.0?. What is (vA)1, the velocity of tennis ball A, immediately before the collision?

Answer 1

The ball will fall freely before the collision under the influence of gravity,

$$ \begin{aligned} v^{2}-u^{2} &=2 g h \\ \left(v_{A}\right)_{1} &=\sqrt{2 g h} \\ &=\sqrt{2 \times 9.8 \times 4} \\ &=8.85 \mathrm{~m} / \mathrm{s} \end{aligned} $$