Problem 1. A 20-kg crate is accelerated by a net force of 50 N applied for 12 s. (a) What is the acceleration of the crate from Newton's second law? (b) If it starts from rest, how far does it travel in the time of 5 s? (c) How much work is done by the 50 N net force? What is the work of the gravity force and normal reaction force? (d) What is the velocity and the kinetic energy of the crate at the end of 4 s? Problem 2. A sled and rider with a total mass of 40 kg are perched at the top of a hill with neatly zero speed, as pictured in the diagram below. The top of this hill is 40 m above the low point in the path of the sled. A second hump in the hill is 30 m above this low point. (a) What will be the kinetic energy and the speed of the sled at the top of the second hump? You can ignore friction in this problems. Use g = 10 m/s for your calculations. (b) A sled and rider with a total mass of 40 kg have kinetic energy 5, 000 J. Find the magnitude of its momentum p. 40 m 30 m Figure 1: Schematic graph for Problem 2.