Question

See how a block and tackle system can increase your mechanical advantage. You will need two broomsticks, a rope, and two helpers.

A. Give each helper a broom stick and have them stand facing each other holding the broomstick firmly in both hands in a horizontal position. The broomsticks should be at the same level, about two feet apart.

B. Tie one end of the rope to one of the broomsticks. (You may need to have one of your helpers hold the knot firmly in one hand as he or she holds the broomstick to help anchor it.)

C. Wrap the rope around the other broomstick, as in a simple pulley system, and pull on the free end of the rope. Your helpers should resist your pulling. What happens? Can you pull the broomsticks together?

D. Now weave the rope back over the first broomstick, so you have a double pulley. Pull on the free end. What happens now? Can you pull the broomsticks together? What is your mechanical advantage?

E. Try weaving the rope over the broomsticks one or two more times. Describe what happens, and state the mechanical advantage of each situation.

F. Write a summary of what happened and an explanation using the terms:

Answer 1

A block and tackle system uses multiple pulleys to increase mechanical advantage. By adding more ropes and pulleys, the effort force required to lift heavy objects decreases. The mechanical advantage increases as the number of ropes supporting the load increases.

Block and Tackle System to Increase Mechanical Advantage

1. Give each helper a broomstick and have them stand facing each other, holding the broomstick firmly in both hands in a horizontal position.
2. Tie one end of the rope to one broomstick and wrap the rope around the other broomstick.
3. With a simple pulley system, pull on the free end of the rope while your helpers resist. Observe how the broomsticks move or do not move.
4. Weave the rope back over the first broomstick to create a double pulley. Pull on the free end and notice the difference in movement.
5. Try weaving the rope over the broomsticks one or two more times and observe how the mechanical advantage changes.

A block and tackle system uses multiple pulleys to increase mechanical advantage, making it easier to lift heavy objects. As the number of ropes supporting the load increases, so does the mechanical advantage. The more pulleys you add, the less effort force you need to exert to achieve the same amount of work.