1. How much pull at P would be required to lift 150 lbs. at W? (Fig. 18.)
2. What force at W would just balance 200 lbs. at P?
3. With what force or how many lbs. is the rope C pulling on its fixed end when 300 lbs. is being lifted at W? (This force or pull is called the tension at C.)
Fig. 20. - A Dumb-Walter Pulley.
Fig. 21. - Tackle or Awning Pulley.
5. How far would the three lower pulleys and frame be raised if the rope at P is pulled down 6 ft.?
6. How does the force of the arrangement shown in Fig. 19 differ from the force obtained from a block and tackle having three pulleys in each block (neglecting friction)?
Fig. 22. - Use of a Single Pulley. Double-platform material elevator for lifting materials to a building. One elevator goes up while the other comes down, so that only force enough to lift the actual load is required.