## PULLEYS

pulleys_jug.html

### Objectives:

To see that the number of strings of a pulley decrease the amount of effort needed to lift an object.

### Time:

One-two class times.

### Materials:

Per group-broom handle,jug with a closed handle filled with sand or water, twine or rope, duct tape.

### Prediction-Hypothesis-Question:

What is the easiest way to lift the jug?

### Procedure:

Have the students tape the ends of the broom handle down between 2 desk tops.
Allow the students to try several ways to lift the jug using the rope and broom handle.
share their results
Day Two:
Now, have the students tie the rope to the broom handle, loop the rope through the jug handle, and lift by the free end of the rope with the weight in the middle(movable pulley).
Loop the rope over the broom handle and pull down on the the free end. Record the effort.
Now loop the rope through the jug handle another time and then up and over the broom handle. You will have 2 loops over the broom and the original not.

### Record Results:

Students share results that they have recorded in their journals.

### Conclusion:

They will see that the more times the rope is looped through the jug and over the broom handle, the less effort needed.

### Extensions:

Find small jugs for the students to pull up with strings and use spring scales to measure the force needed.

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