10. A 10 kg rock falls 5 meters and hits the ground. Did the rock have any energy just before it hit the ground? If so, how much? What force did it require, to get the rock to start
moving?

What are the phases shown in a and d called?

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

Given the position vector of the particle r(t)=(t+1)i+(t^2−1)j+2t k, find the particle's velocity and acceleration vectors at t=1