Question

A 20-kg child on a swing can make a maximum angle of 400 with respect to the vertical. What is the child’s maximum speed if the chains of the swing have a length of 4 m?

Answer 1

$h=4-4\cdot\cos40°=0.94\ (m)$

$mgh=mv^2/2\to v=\sqrt{2gh}=\sqrt{2\cdot9.8\cdot0.94}=4.3\ (m/s)$