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 $ m{{s}^{-1}} $
• B. 10 $ m{{s}^{-1}} $
• C. 15 $ m{{s}^{-1}} $
• D. 17 $ m{{s}^{-1}} $

Answer 1

Answer: (A)

According to law of conservation of energy $ \frac{1}{2}mv_{\max }^{2}=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\,m{{s}^{-1}} $