## Levers, Pulleys and Rigging

Materials :

• string or cord
• bamboo skewers or small sticks
• tape
• small pulleys or thread spools
• spring scale
• coat hanger wire
• masking tape or duct tape
• 16d nail
• drinking straw
• scissors
• Activity 1.2.2 Student Worksheet
• metric weights

Procedure :
Block and Tackle

1. Obtain some small pulleys or make pulleys from thread spools.
[See Figure 1]
2. Thread a string over a single fixed pulley. Hang a known weight
on one end. With a spring scale, pull hard enough on the other string
end to lift the weight. Record the pull force shown on the spring scale.
[See Figure 2]

Pull Force:
3. Thread a string around a single movable pulley. Hang a
known weight on the pulley. Pull on the string hard enough
to lift the weight. Record the pull force shown on the spring scale.
[See Figure 3]

Pull Force:
4. Thread a string over a fixed pulley and a movable pulley. Hang a known weight on one end. With a spring scale, pull hard enough on the other string end to lift the weight. Record the pull force shown on the spring scale. [See Figure 4]

Pull Force:
5. Thread a string over two fixed pulleys and a movable pulley. Hang a known weight on one end. With a spring scale, pull hard enough on the other string end to lift the weight. Record the pull force shown on the spring scale. [See Figure 5]

Pull Force:
6. Thread a string over more fixed pulleys and movable pulleys. Hang a known weight on one end. With a spring scale, pull hard enough on the other string end to lift the weight. Record the pull force shown on the spring scale. [See Figure 6]

Pull Force:

Block and Tackle Conclusion :
Do you gain mechanical advantage by using more that three pulleys to compound the force? Why or why not?

***********************

Procedure:
Booms, Cranes and Derricks

1. Make a square base and upright stand by taping wood sticks together as shown.
[See Figure 7]
2. Balance a ruler or meter stick on the top. [See Figure 8]
What machine is this line?
3. Now slip a section of drinking straw on the 16d nail and attach it
between the uprights. [See Figure 9]
4. Add a lever arm by taping a stick to the drinking straw. [See Figure 10]
5. There are two ways to arrange the ropes which support the lever and the hanging load.
[See Figure 11]
6. We often see pulley blocks at A, B, C and D. [See Figure 12] Build one of these rigs out of ruler size sticks of wood and see which works best for you. Remember our task is to dangle something over the side of the desk and then hoist it back up.

Conclusion :
Brainstorm with you group applications of rigging (block and tackle, booms, cranes and derricks) on ships. List your ideas here.

Student Worksheet #1.2.2