Question

4. A 175 N force acting at 15 ◦ above the horizontal pulls a 85 kg box through a distance of 8 m along a horizontal surface. If the coefficient of kinetic friction between the floor and the box is 0.2, how muck work done is done by: (a) applied force? (b) normal force? (c) friction? (d) gravity?

6. A 45 kg skier rides a lift straight to the top of a hill. The path of the lift is 2830-m-long and makes an angle of 30 ◦ with the horizontal. What is the change in the skier’s gravitational potential energy?

2. A woman, holding a dumbbell in each of her outstretched arms, stands at the center of a platform that is rotating at 3 rads/s. With her arms outstretched, the total moment of the rotating system is 2 kgm2. While the woman and platform rotate, the woman suddenly tucks her arms in and up to her body. After doing so, the moment of inertia of the system drops to 1 kgm2. Approximately, what is the angular speed of the woman after she tuck her arms in?

Answer 1