Question

A pendulum is raised 0.7m above the floor, is released and then swings freely. Neglecting all frictional forces, what is the velocity of the pendulum when it is 0.25 m above the floor?

Answer 1

According to law of conservation of energy, the potential energy between 0.7 and 0.25 m converted to the kinetic energy:

$$mg(H-h)=\frac{1}{2}mv^2,\\ \space\\ v=\sqrt{2g(H-h)}=2.97\text{ m/s}.$$