Question

A child is swinging a swing. Minimum and maximum heights of swing from earths surface are $ 0.75\,m $ and $2\,m $ respectively. The maximum velocity of this swing is

• A. $5\,ms^{-1}$
• B. $10\,ms^{-1}$
• C. $15\,ms^{-1}$
• D. $17\,ms^{-1}$

Answer 1

Answer: (A)

According to law of conservation of energy
$\frac{1}{2}mv^{2}_{\max }=mg(h_{2}-h_{1})$
$\Rightarrow v_{\max}=\sqrt{2g(h_{2}-h_{1})}$
$ =\sqrt{2 \times 10 \times (2-0.75)}$
$ =\sqrt{2 \times 10 \times 1.25}$
$=\sqrt{25}=5\,ms^{-1}$