Question

1. A 2 kg ball moving at 2 m/s collides with a stationary 1 kg ball. What is the speed of the 1 kg ball after the collision if the collision is:
(a) elastic, and the speed of the 2 kg ball drops to 1 m/s?
(b) inelastic?

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?

3. During a tug-of-war, team B pulls on team A by applying a force of 300 N to the rope between them. If team B pulls team A through a distance of 5 m, how much work is done by:
(a) team A?
(b) team B?

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?

7. How much energy is stored by a spring, with a spring constant of 3 N/m, when it is compressed by 20 cm?

Answer 1

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