1. a. Which has more potential energy, a 10-kg box on a shelf or a5-kg box on a shelf that’s twice as high? Explain.

   b. Which has more kinetic energy, a 2000-kg car traveling downthe road or a 1000-kg car traveling twice as fast? Explain.

2. If your friend pushes a lawnmower six times as far as you dowhile exerting one half as much force, which one of you does morework? How much more? Explain.

3. a. A car has a certain amount of kinetic energy when it’s movingat 40 mph. If it speeds up until it’s going at 80 mph (two timesfaster), how many times more kinetic energy does it have?Explain.

   b. If the stopping distance for the car at 40 mph was about 75ft, what is the stopping distance when it’s going two times faster?(Assume the stopping force stays the same. Keep in mind that Work,which is force × distance, is equal to the change in kineticenergy.)

4. An apple hanging from a limb has potential energy relative tothe ground because of its height. If it falls, what has become ofthis energy just before it hits the ground? What has become of thisenergy after it hits the ground? Explain.

5. A roller coaster car has a potential energy of 10,000 J(relative to the ground) at the top of a certain hill, where it’salmost motionless. Then it rolls down the track. Explain youranswers to these questions, assuming friction and air resistancecan be neglected.

   1. The bottom of the hill is right at ground level. When the cargets there, how much potential energy and how much kinetic energywill it have?

   2. The car goes up another hill which is 3/4 as high as theoriginal hill. How much potential energy and kinetic energy willthe car have at the top of this second hill?

   3. The car goes down the second hill, where once again the trackreaches ground level. How much potential energy and kinetic energywill the car have there?