1. Pulling a banner behind itself, an airplane exerts a force of 120 newtons over a distance of 550 km. How much work does the airplane do on the banner?

2. Using a block-and-tackle, a mover takes up 18.5 m of rope to raise a 115-kg stove from the ground to a window ledge 3.7 m high. What force must he exert on the rope if the efficiency of the block-and-tackle is 63 percent?

3. A seesaw is a lever. Suppose you use a seesaw to lift a bucket of sand. What is the ideal mechanical advantage of the seesaw if the efficiency of the seesaw is 67 percent, the effort force is 36 N, and the resistance force is 144 N?