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1. In Fig. 3–2A, a force of 80 pounds is exerted at W; l = 12 inches and L = 32 inches. Find the value of force F required to balance the lever.

2. In Fig. 3–2B, a weight of 90 pounds is supported at W; l is 10 inches. The total length of L of the lever is 25 inches. Find the value of F.

3. In Fig. 3–2C, F = 28 pounds; L = 10 inches, A = 24 inches. What is the weight supported at W?

4. The radius of a roller on which is wound the lifting rope of a windlass is 4 inches. What force must be exerted at the end of a crank arm 24 inches in length attached to the shaft to lift one ton (2,000 pounds)? W = 2,000; R — 24; r = 4 (Fig. 3–3).

5. In Fig. 3–4 is shown a block and tackle. The pulleys turn freely on a pin. There are three parts of rope. If 90 pounds is to be lifted, what force is required at the end of the rope F?