PhysicsLAB Amusing Problems
The Pet Rock

Even though Dr. J is close to being stone broke, he takes a trip to Boulder, Colorado, to pick up his new pet rock (think about it). He bought it from a mail-order catalog, "Hard Things to Buy and Sell." Little does he know what he is in for. The catalog price is $1.98 plus a delivery charge of $200.00. Therefore, Dr. J decides to travel to Boulder to pick it up himself in order to save the delivery charge. When he arrives, he is shocked to learn that his "pet" weighs 1000 Newtons! (I guess he took it for granite that it would fit in his pocket.) After renting a truck, he decides to use his knowledge of physics in order to load it. He uses a small rock as a fulcrum and a long pipe as a lever with which to pry the rock. Try as he might, however, he can't apply enough torque to budge the boulder. Fortunately for Dr. J, a local elephant named Nate comes along. Nate easily lifts the rock 1.2 meters into the bed of the truck. (The obvious moral of this story is "Better Nate than lever.")
 
If Nate charges $50 per kilowatt-hour, how much does Dr. J have to pay for the work that Nate did? 

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