OBJECT:

To compare the MECHANICAL ADVANTAGE, and the direction of EFFORT and RESISTANCE in a combination of a fixed and movable pulley.

MATERIALS:

* CAUTION *

This experiment has the potential of eye injury !! Be sure to wear your Safety Goggles at all times.

Safety goggles, Set of weights, Set of heavy books to be placed at the base of the stand,, Rubber band scale, Twine, Two foot PVC stand, with 4 inch PVC extension with bolt and wing nut, Two pulleys, Two foot with metric strip, Large nut.

PROCEDURE AND OBSERVATION:

Be sure to ware your Safety Goggles.

1. Be sure to adjust the Rubber band scale to zero.

2. Construct the set up shown in the diagram.

3. Pull on the Rubber band scale until the resistance is no longer resting on the table. Record the number of grams indicated on the Rubber band scale.

4. Repeat step number 3 using the weights shown below, and record the effort needed to lift the resistance.

5. Now, using a large nut, with a piece of string tied to the nut, so that you can attach the paper clip to it. ( Do not use the Rubber band scale for this. ) Attach it to the bottom pulley, place your Two foot metric strip, in back of the first combination of pulleys, pull straight down on the twine ( string ), so that both sides of the string are parallel, with out lifting the large nut, record the height of the knot of the twine loop. ________cm. Now, raise the resistance so that the bottom of the Large nut is 10 cm high. Now record the new height of the knot of the twine loop. ________ cm. Subtract the second height that you got from the first height. What is your answer? _________ cm.

6. Now, construct the second combination of a fixed and movable pulley.

7. Pull up on the Rubber band scale until the resistance is no longer resting on the table. Record the number of grams indicated on the Rubber band scale, in the table below.

8. The object now, is try to measure the distance that the Resistance moves and the distance that the Effort moves.

9. Now, using your Large nut ( Do not use a Rubber band scale for this.) with your Two foot metric strip in back of the second combination of pulleys ( B ), pull straight up on the twine, so that both sides of the twine are parallel; With out lifting the weight, record the height of the knot of the twine loop. _______cm. Now, raise the Resistance so that the bottom of the weight is 10 cm high. Now, record the new height of the knot of the twine loop. _______cm. Subtract the first height that you got from the second height. What is your answer ? ______ cm.

QUESTIONS:

1. What are the formulas for finding the Mechanical Advantage ?

2. Using the table ( A ) what is the M. A. or the first combination of pulleys?

3. Using table ( B ) what is the M. A. for the second combination of pulleys?

4. What is the direction of Resistance and Effort in a first combination: and in a second combination ?

5. Find the M. A. using the information in step # 5 ( above ).

6. Find the M. A. using the information in step # 9 ( above ).

7. When force is gained, what happens to the distance? Explain.

8. Which combination of pulleys has the greater M. A. ?

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