Materials: 100 Cm Lever, Fulcrum, Spring Scale, Weight

Simple Machines

Station 1: Levers

Materials: 100 cm lever, fulcrum, spring scale, weight

Question: What is the effect on work when you change the distance from the fulcrum to the input force on a lever?

Hypothesis: What do you believe the effect on work will be?

Draw the following data table in IAN.

Length of Length of Length of Input Force (N) Work Lever Resistant Arm Effort Arm D x F = J 100 cm 20 cm 80 cm 100 cm 40 cm 60 cm 100 cm 60 cm 40 cm 100 cm 80 cm 20 cm

Procedure: 1. Place the meter stick on desk so that 80 cm is off the edge and the textbook is on top of the other end – even with the edge. 2. Tie a string around the end of the lever 2 cm from the end that is off the table. 3. Connect the spring scale to the string. Pull down on the spring scale to cause the lever to lift the weight 3 cm (.03 m) off the table. Record the force in N on your data table (Input Force) 4. Multiply distances (m) and force (N) to find work (Joules) 5. Repeat steps 1-4 with the other resistance/effort arm lengths.

Analysis:

1. How does the effort change when you use a longer resistance arm? 2. What would happen if you left the resistance arm the same length and made the lever longer?

Conclusion: 1. What is the effect on work when you change the ratio of resistance arm to effort arm? 2. What is the effect of changing the length of the lever? Station 2: Incline plan

Materials: ramp, spring scale, mass.

Question: What happens to the amount of work needed to move an object when the height of the incline plane increases?

Draw the following data table: Distance (m) Height (m) Force (N) Work (F x D = J) 1 m 1 m 1 m

Procedure: 1. Place three books in a stack on the table. 2. Place one end of a ramp on the stack of books. 3. Attach the mass to the spring scale and pull slowly up the ramp. 4. Record the force (N) on your data table. 5. Calculate work (J) by multiplying force times distance. 6. Change the height of the ramp and repeat steps 1-5.

Analysis and Conclusion:

1. What happens to the amount of work needed to move an object when the height of the incline plane increases ?

2. How can you apply this conclusion to helping disabled people enter buildings? Station 3: Wheel and axle

Materials: Metal can, 3 paper clips, string, straw, mass to lift.

Question: How do you find the mechanical advantage of a wheel and axle?

Hypothesis:

Procedure: 1. Tape a string to the long end of a straw. 2. Attach two paper clips to can with tape. They need to be far enough up to allow the straw through easily. 3. Insert straw through both paper clips 4. Attach mass to string with paper clip. 5. Determine mechanical advantage of your wheel and axle. (Divide the wheel diameter by the axle diameter). 6. Use your wheel and axle to lift the mass. 7. Determine how many joules of work are completed. Attach the mass to the spring scale and determine force in joules to lift. Determine distance mass is lifted. Calculate work.

How can you increase the mechanical advantage of your wheel and axle machine? Station 4: Pulley

Materials: Block and tackle (2 pulley) set up, mass, spring scale, ruler, calculator.

Question: How does a movable pulley affect the amount of work required to lift an object?

Draw this Data Table in IAN: Distance (m) Force (N) Work (J) Countertop to pulley Without pulley With fixed pulley With movable pulley

Procedure: 1. Use the spring scale to lift the mass. Record the force (N) required to lift the mass on the data table. 2. Connect the mass and spring scale to the block and tackle. (See diagram in textbook or your teacher for details) 3. Measure distance from mass to bottom of pulley. Record this distance in data table for both without and with pulley. 4. Pull the spring scale and record force required to lift the mass with the pulley. 5. Record force required with pulley in the data table.

1. How does a pulley affect the amount of work required to lift an object? 2. How does the mechanical advantage of a fixed pulley compare to your movable pulley?

Materials for each groups:

50 cm stick 1 meter stick Spring scale Ruler Metal can 3 paper clips Straw String Mass 2 pulleys