Question1
A 100-kg athlete is performing vertical leap to test his leg strength. He leaves ground at 3.20 m/s, zooms upward to some highest altitude, and then returns to the ground. As he lands, he bends his legs and crouches down, so that he moves 30 cm downward as he comes to a stop.
What average force did athlete’s legs apply on a ground as he landed?
Question2
A 45.0-kg girl is standing on a 134-kg plank. The plank, initially at rest, is free to slide on a frozen lake that is a flat, frictionless surface. The girl begins to walk along plank at a constant velocity of 1.60 m/s to the right relative to plank. (Let the direction the girl is moving in be positive. specify direction with the sign of your answer.)