[10] (3) A stalent of mass -- 63 kg falls freely from rest and strikes the ground. During 7 the collision with the ground, he comes to rost in a time of 0.01 s. The average force exerted on him by the ground is +18000 N. where the upward direction is taken to be the positive direction. From what height did the student fall? Assume that the only force acting on him during the collision is that due to the ground