I got most of it except for part B and C?

Question

A 50.0-g object connected to a spring with a force constant of 35.0 N/m oscillates on a horizontal, frictionless surface with an amplitude of 4.00 cm. Find (a) the total energy of the system and (b) the speed of the object when the position is 1.00 cm. Find (c) the kinetic energy and (d) the potential energy when the position is
3.00 cm.

Answer 1

OK, you already know (a), which is the total energy. At the peak displacement (which is the amplitude), all the energy is potential energy PE, in the form of spring deformation. PE = .5*k*x^2 = .5*35*.04^2 = .028 j. At other times, the energy is divided between PE and kinetic energy KE, and PE+KE=.028. So for (b), KE = .028-.5*35*.01^2 = .02625 j. Then the velocity = sqrt(2*KE/m) = 1.025 m/s. For (c), KE = .028-.5*35*.03^2, and for (d) PE = 5*35*.03^2.