Student Exploration Levers (answers)

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Levers

Vocabulary: effort, first-class lever, fulcrum, lever, load, mechanical advantage, second-class lever, third-class lever

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

1. A lever is a rigid plank or bar that pivots on a fulcrum. Look at the lever in the picture. Where would you push on the lever to lift the rock?

2. Where are some places that you see levers in everyday life?

Gizmo Warm-up

In the Levers Gizmo™, the strongman tries

to lift animals by pushing down or pulling up

on the lever. The force of his push or pull is

the effort. The weight of the animal is the

load. Both forces are measured in newtons.

 You can move the fulcrum to the left or right by dragging it.

 You can drag animals to any spot on the lever.

 You can move the strongman by dragging him.

 You can change the strongman’s Effort with the slider.

1. Drag the pig to the lever. Try to arrange the lever so that the strongman can lift the pig. What did you do so that he could lift it?

2. Did the strongman pull up or push down to lift the pig

3. How much effort was needed to lift the pig

Question: In a first-class lever, the fulcrum is between the effort (strongman) and the load (turkey). How are first-class levers helpful?

1. Observe: Place the turkey, strongman, and fulcrum at a variety of positions. Each time, pay attention to the smallest amount of Effort needed to lift the turkey. (Note: In this simulation, the lever itself has no mass.)

2. Form hypothesis: When does a lever make it easiest to lift the turkey?

3. Experiment: Place the fulcrum at position 3, the turkey at position 4, and the strongman at position 2. Slowly increase the Effort until the turkey is lifted

A. What is the smallest force that can lift the turkey

B. How does this effort compare to the turkey’s weight

4. Revise and repeat: Move the strongman further away from the fulcrum and lift the turkey.

A. What is the smallest force that can lift the turkey now

B. Which moves more, the turkey or the strongman’s hands

5. Draw conclusions:

A. How does a first-class lever help you lift a turkey?

B. What is the “price” that you pay for using less force?

6. Predict: What will happen if the turkey is farther from the fulcrum than the strongman?

7. Test: Check your prediction using the Gizmo. Were you correct

Question: How are forces and distances related?