1. The equation of motion for an object of mass 0.4 kg in SHM is given by

X = 9.2 cos(3.9t) (all SI units)

Calculate its kinetic energy when the mass is a third of the amplitude away from the equilibrium position.

2. A vertically hanging spring is extended by a length of 24.3 mm when a mass of 7.28 kg is suspended at equilibrium from its end. If the mass is displaced from equilibrium, what will be the frequency of vibration

3. A spring is vertically suspended. When a mass 0.84 kg is attached to the free end of the spring, the spring extends a length of 9.7 cm down to its equilibrium position. The mass is then pulled down a further 3.6 cm and released. Find the time it takes to first reach back to the equilibrium position.