Problem 7: A uniform disc of mass 30 kg and radius 0.5 m 1s attached to a spring of stiffness 200 N/m. The unstretched length of the spring 1s lo = 1 m and the disc rolls without slipping on the ground (note that this means friction exists between the disk and the ground). (a) Find the equation of motion of the disk. The equation of motion should only mvolve the variable x and its derivatives. Note that 8 can be taken to be 0 when the spring was unstretched. o 2 k Ans: X = =-x im