1. What amount of work is done when a force of 50 N is used to drag an object a distance of 20 meters across a floor? 2. What's the kinetic energy of an object that has a mass of 12 kilograms and moves with a velocity of 10 m/s?

3. A skateboarder is inside of a half-pipe, shown here. Explain her energy transformations as she jumps off at point A, slides to point B, and finally reaches point C.

4. If the skateboarder continues going back and forth on the half-pipe, she'll eventually come to a stop at the bottom automatically. Explain why, in terms of her energy.