Question

A tennis ball is dropped on to the floor from a height of $9.8\, m$. It rebounds to a height $5.0\, m$. Ball comes in contact with the floor for $0.2 \,s$. The average acceleration during contact is ___$ms ^{-2}$. $\left(\right.$ Given $g =10\, ms ^{-2}$ )

Answer 1

$v _{ i }=\sqrt{2 gh _{ i }} $
$ =\sqrt{2 \times 10 \times 9.8} \downarrow $
$ =14\, m / s \downarrow$
$ v _{ f }=\sqrt{2 gh _{ f }} $
$ =\sqrt{2 \times 10 \times 5} \uparrow$
$ = 1 0 \,m / s \uparrow$
$\left|\vec{ a }_{ avg }\right|=\left|\frac{\Delta \vec{ v }}{\Delta t }\right|=\frac{24}{0.2}=120 \,m / s ^2$