A ball dropped from a height of $90 ext{ m}$ hits a floor and loses one-tenth of its speed at the c

Question

A ball dropped from a height of $90	ext{ m}$ hits a floor and loses one-tenth of its speed at the collision. What is its speed just after the first collision? (Take $g = 9.8	ext{ m/s}^2$)

Professor PC Thomas Classes · Answer

The speed before impact is $42	ext{ m/s}$. It loses one-tenth of its speed ($4.2	ext{ m/s}$). Therefore, the speed just after the collision is $42 - 4.2 = 37.8	ext{ m/s}$.