The motion of a 3.0 kg mass on the end of a spring is described by
x(t) = (0.20 m)*Cos(2t/3.0s).
What is a time when the system is at the equilibrium position?

Please explain how to find this answer

Suppose that a mass of 2 kg is attached a spring whose spring constant is 50. the system is damped such that b = 12 . the mass is set in motion with an initial velocity of -8 m/s at a position 0 meters from equilibrium. set up and solve a differential equation that models this motion. write your solution in the form a cos ( ω t − α ) where α is a positive number. use your solution to fill in the information below: what is the amplitude of the motion? what is the value of ω ? what is the phase shift?