The position of a 60 g oscillating mass is given by x(t)=(2.0cm)cos(10t), where t is in seconds. determine the velocity at t=0.40s.

The position of an oscillating mass is given by:

where A is the amplitude of the oscillation, the angular frequency and t the time.

The velocity of the oscillating mass can be found by calculating the derivative of the position:

In this problem, A=2.0 cm and , so if we substitute these data and t=0.4 s we can find the velocity at t=0.4 s: