Question

A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how high can the ball bounce back? $(g=10m{s}^{-2})$

• A. 6 m
• B. 10 m
• C. 3 m
• D. 12 m

Answer 1

Answer: (A)

6 m

let,m$=$mass of the ball
potential energy at height of 10m$=mgh=\left(100m\right)Joule$
now at striking the ground it loses 40% of its energy
i.e;$\frac{40}{100}\times 100m$ joule
$=$(40m)joule
now potential energy left in ball$=100m-40m=60m$ joule
now,mgh$=60m$,g$=10m{s}^{-2}$
$h=\frac{60}{10}$
h$=$6m
hence,the ball will bounce back up to 6m.