Energy Conversion

The Basic Answering Technique

This science revision note aims to help your child get the proper answering technique for energy conversion.

 

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Jacob and Dylan each held a basketball in their hand, as shown in the diagram below. Both basketballs are identical. They then took turns removing their hands from under the ball to let it drop naturally. They compared the loudness of the sound made when the basketballs landed on the floor.

Whose basketball made a louder sound? Explain why.

 

STEP 1

Identify the energy conversion that takes place for the balls to make a sound when they land on the floor.

Gravitational potential energy (of the basketball) —> Kinetic energy (as the basketball is falling) —> sound energy (when the basketball hits the floor)

 

STEP 2

Identify which type of energy was changed and how it was changed.

To do this, you have to identify what is the changed variable when Jacob and Dylan were letting the ball drop.

Looking at the diagram, you can see that Dylan’s basketball is higher above the ground than Jacob’s basketball. Hence, the height of the basketball is the changed variable.

 

So which type of energy does the height of the basketball affect? Gravitational potential energy.

The greater the height of the basketball, the greater the gravitational potential energy. Therefore, Dylan’s basketball has more gravitational potential energy.

 

STEP 3

Explain how the change in Step 2 affects the sound made when the basketballs land on the floor. Use the energy conversion you identified in Step 1 in your explanation.

More gravitational potential energy (of the basketball) —> More kinetic energy (as the basketball is falling) —> More sound energy (when the basketball hits the floor)

Therefore, Dylan’s basketball made a louder sound when it landed on the floor.

 

FINALLY, put your answer together

Question: Whose basketball made a louder sound? Explain why.

Answer: Dylan’s basketball made a louder sound.

Evidence: Dylan’s basketball was higher above the floor compared to Jacob, so the basketball had more gravitational potential energy.

Reasoning: As the basketball in Dylan’s hands is falling, more gravitational potential energy is converted to more kinetic energy of the basketball.

When the ball hits the floor, more kinetic energy of the basketball is converted to more sound energy. 

 

Take note:

Those highlighted in yellow are the description of a situation.

Use comparative words such as more

 

Read the revision notes on common mistakes on energy conversion for detailed explanations.

>> https://scienceshifu.com/common-mistakes-on-energy-conversion/

 

 

Common mistakes

 

Wrong answer: Dylan’s basketball made a louder sound. Dylan’s basketball was higher above the floor compared to Jacob, so it had more gravitational potential energy. More gravitational potential energy is converted to more kinetic energy and then to more sound energy when the ball hits the floor.

The explanation is unclear. When you say “more gravitational potential energy is converted to more kinetic energy and then to more sound energy”, it is unclear which type of energy is converted to sound energy. You need to specify that it is kinetic energy that is converted into sound energy.

Hence, you should split your explanation into separate sentences to make it clear:

1) More gravitational potential energy is converted to more kinetic energy

2) More kinetic energy is converted to more sound energy

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Andy Ling

Guiding your child to be the master of science concepts

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