A 0.650 kg block slides on a frictionless, horizontal surface with a speed of 1.19 m/s. The block encounters an unstretched spring and compresses it 25 cm before coming to rest. (a) What is the force constant of this spring? ____ N/m (b) For what length of time is the block in contact with the spring before it comes to rest? ___s For part a: Since the formula for a force constant is f=-kx, and the problem doesn't give a k value, I tried solving for it using: k=(mg)/x and got k=(.650kg*9.81)/.25 m k=25.50g and plugged this in to f=-fx and got f=-6.3765 For part b: im not even sure where to start ..