## Saturday, May 7, 2011

### What is a Lever?

A LEVER is a simple machine that is a bar (lever arm) resting on a turning point (fulcrum)

A lever is used to move or lift things.

Example: seesaw

Vocabulary: machine, lever, lever arm, bar, fulcrum, turning point

Materials

• ruler (lever arm)
• rectangular eraser (fulcrum)

Activity 1

Directions

• Have students place a ruler (lever arm) on top of an eraser (fulcrum) so that the eraser is under the middle of the ruler. (The ruler will be balanced.)
• Have students stack 5 pennies on one end of the ruler.
• Challenge the students to raise the pennies without touching the pennies. (They need to press down on the opposite end of the ruler.)
• (Explain that the ruler is acting as a lever when they press down on the other end and it lifts the pennies.)
• Try the same activity but place the 5 pennies on the other end of the ruler.
• Challenge the students to raise the pennies without touching them.
• Have the students explain why they were able to lift the pennies without touching them.

Activity 2

Directions

• Have the students place 3 pennies on one end of the ruler.
• Ask them to predict the minimum number of pennies that would have to be placed on the other end of the ruler to raise the 3 pennies. (They could write down their prediction.) (Answer: 3)
• Have the students add pennies to the other side to test their prediction.
• Were they correct? Why?
• Try the same experiment with 7 pennies.

Activity 3

Directions

• Have students place 3 pennies on one end of the ruler and 6 pennies on the other end of the ruler.
• Challenge the students to lift the end with 3 pennies without adding or taking away pennies on either end.
• If students are having trouble tell them that they can move the pennies but must keep 3 on one side of the ruler and 6 on the other side of the ruler.

This can be accomplished by moving the heavier pile of pennies towards the fulcrum.

Activity 4

• Have students sketch/draw and label a seesaw (including the bar/lever arm and turning point/fulcrum.
• Have students sketch pictures of today's 3 previous lever activities in their science notebooks and explain how the lever worked in each activity.
• Have students visit a park and enjoy a real seesaw (a lever)! Have fun!

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