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Simple Machines and Catapults

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Simple Machines and Catapults

A class is testing a small, safe catapult that launches a soft pom-pom into a target zone. Use the information on this sheet to explain how simple machines and forces affect its motion. Assume each launch uses the same pom-pom and the same pulling force unless stated otherwise.

Read the test notes

Hemi built a catapult with a lever arm. She pulled the arm down, held it briefly, then released it. The bent arm and stretched elastic stored elastic potential energy. On release, that stored energy transferred mainly into the pom-pom’s kinetic energy. Some energy also spread to the surroundings as sound and heat. In three trials, the pom-pom travelled 2.4 m, 2.6 m and 2.5 m. Hemi changed only the launch angle between test sets. A fair test changes one factor at a time and measures the same outcome each time.

1.Which simple machine is the main part of this catapult? Choose the best answer.

Lever
Pulley
Screw
Inclined plane

2.Use this description: the lever arm turns around a fixed pivot; the pulling force is applied to the arm, and the pom-pom rests in a cup at the opposite end. Identify the fulcrum, effort and load. State where each is found.

3.The lever arm turns around a pivot. What does the pivot do?

It acts as the fulcrum
It stores the pom-pom’s kinetic energy
It removes all friction
It changes the pom-pom into a different material

4.Match each simple machine to its usual job.

Pulley
Inclined plane
Screw
Wedge

Provides a sloping surface to move a load to a higher or lower level
Has a sharp edge that can split or cut
Uses a spiral thread to fasten or lift
Changes the direction of a pulling force, often to lift a load

5.Complete the energy story: Before release, the pulled-back catapult stores energy. As the pom-pom launches, much of this changes into energy.

6.Hemi’s three distances were 2.4 m, 2.6 m and 2.5 m. Calculate the mean distance travelled. Show your working.

7.Hemi wants to find out how launch angle affects distance. Name one factor she should keep the same in every test, and explain why.

8.A second test set uses a steeper launch angle. Predict one possible change to the pom-pom’s path, and explain why its landing distance might change. There is not enough information to calculate an exact distance.

9.True or false: A catapult creates energy from nothing when its arm is released. Correct the statement if it is false.

TrueFalse

10.A teammate says, “A longer lever arm will always make the pom-pom travel farther.” Explain why this claim needs testing rather than being accepted as certain.