Question

From a height of 5m a ball is thrown vertically downwards with an initial velocity of 10m/s towards a hard horizontal floor. If it bounces to the same height the coefficient of restitution is $(g=10m{s}^{-2})$

• A. $\frac{1}{2}$
• B. $\frac{1}{\sqrt{2}}$
• C. $\frac{1}{4}$
• D. $\frac{2}{3}$

Answer 1

The correct option is B $\frac{1}{\sqrt{2}}$


$e=\frac{v_2-v_1}{u_1-u_1}{u}_2=0,v_2=0,u_1=?,v_1=?u_1^2=u^2+2gh{u}_1=\sqrt{100+2\times 10\times 5}=10\sqrt{2}m/s{v}_1=\sqrt{2gh}=\sqrt{2\times 10\times 5}=10m/s\therefore e=\frac{-10}{10\sqrt{2}}=\frac{1}{\sqrt{2}}$