Experiments
Click on the following to get to the experiment directions. There are additional experiments in the links on the Resources page.
Lever Wedge Pulley Inclined Plane
Materials:
Several large books
Two cups of dried beans in a small zip
top plastic bag
ruler
rubber band
Procedure:
Stack
several books on your desk. Prop a final book so that one end rests on the book
stack, and the other rests on your desk.
Tie your rubber band around the top of
your bag of dried beans.
Lift the bag of dried beans straight up
from the desktop to the top of the book stack. Measure the length of the rubber
band. Record in your journal.
Now place the bag of dried beans at the
bottom of the ramp you made with your books. Drag the bag of beans up the
ramp. When the bag is just about at the top of the ramp, measure the length of
the rubber band. Record this measurement in your journal as well.
Something to think about:
What happened to the rubber band during each trial? What explains the difference? Post your conclusions to the discussion forum.
Materials:
hammer
nails
bolts
pieces of scrap wood
Procedure:
Use
the hammer and try to hammer a bolt into the piece of wood
Now repeat, using the nail
Something to think about:
What happened when you tried to hammer
the bolt into the wood?
What happened when you hammered the
nail into the wood?
Examine both a nail and a bolt. What
made the difference?
Post your answers to the
discussion
forum.
Materials:
cardboard rectangle, 10 cm by 15 cm
masking tape
meter stick
2 plastic cups
modeling clay
marbles
Data recording chart
Procedure:
1. Draw two lines across your cardboard rectangle to divide it into three sections, each 5 centimeters by 10 centimeters. Fold the cardboard along these lines.
2. Tape the long edges together to make a triangular tube. This tube is your fulcrum. (Picture A)
3. Tape one cup at each end of a meter stick. Put a ball of modeling clay that's 2 centimeters in diameter in one of the cups. Place the fulcrum 20 centimeters from the end with the empty cup. (Picture B)
4. Drop marbles into the empty cup, one at a time, until the lever balances. Record the number of marbles in your chart. (Picture C)
5. Take the marbles out of the cup and move the fulcrum so that its 30 centimeters from the end of the meter stick with the empty cup.
6. Repeat step 5 with the fulcrum at 30, 40, and 50 centimeters.
Something to think about:
Where was the fulcrum when you needed
the fewest marbles to balance the lever? The most marbles?
If you want to use a lever to lift a
heavy weight, where would you place the fulcrum to make the job easier?
Post your responses to the discussion forum.
Materials:
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Procedure:
1. Make a single fixed pulley. Place a pencil through a spool. Use 2 pieces of twine to attach the pencil to a meter stick that is supported between 2 desks. (Picture A)
2. Stick a metric ruler in clay to stand it up. Center the ruler under the meter stick.
3. Run a piece of twine over the spool. Tie a sinker to one end of the twine and the spring scale to the other end. (Picture B)
4. Pull down on the spring scale to raise the mass 10 cm. The force needed to raise the sinker is the applied force. Record the applied force shown on the spring scale. Then take apart your pulley.
5. Make a single movable pulley. Attach a sinker to a spool with twine.
6. Attach another piece of twine to the meter stick, and tie a spring scale to the other end of the twine. (Picture C)
7. Practice balancing the spool and the attached sinker on the twine. Pull up on the spring scale to raise the mass 10 cm. Record the applied force.
Something to think about:
Compare the applied force needed to
lift the sinker with the two pulleys. What does the difference mean?
How would using a combination of
pulleys affect the applied force?
Post your answers to the discussion forum.