P6 Energy Conversion Topic

Wooden Block Sliding Down the Ramp

This science revision note aims to help your child:

– Understand how potential energy changes at different positions

– Take note of the clues in the question (have you spotted them?)

– Take note of the scientific keywords

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Ava set up a slope on the ground as shown below. The slope is held up by 3 identical blocks. P, Q and R are points on the slope. Ava places a wooden cube at Point Q, then releases it to let it slide down the slope. The wooden cube stops at Point S on the ground.

Which of the following statements is true?

1) The wooden cube has more gravitational potential energy at Point R compared to Point Q.

2) The wooden cube has the most kinetic energy at Point R compared to the other points.

3) If the setup had 2 identical blocks instead of 3, the wooden cube would have slid further than Point S.

4) If the wooden cube had been released at Point P instead of Point Q, the wooden cube would have slid down slower.

STEP 1

Identify the energy conversion taking place.

At Point Q, when Ava places the wooden cube there, the cube has gravitational potential energy.
When she releases the cube, gravitational potential energy is converted to kinetic energy in the cube as it slides down the slope
The cube stops at Point S when all kinetic energy is converted to heat and sound energy

Hence, the energy conversion of the wooden cube is:

Gravitational potential energy –> kinetic energy –> heat energy and sound energy

STEP 2

Let’s evaluate each option to determine if it is true by considering energy conversion.

OPTION 1

“The cube has more gravitational potential energy at Point R compared to Point Q.”

Point R is lower than Point Q, so gravitational potential energy in the wooden cube is converted to kinetic energy as the wooden cube slides from Point Q to Point R. Hence, the wooden cube has less gravitational potential energy at Point R compared to Point Q.

This option is wrong.

OPTION 2

“The cube has the most kinetic energy at Point R compared to the rest of the points.”

As mentioned in the previous point, gravitational potential energy in the wooden cube is converted to kinetic energy as the wooden cube slides from Point Q to Point R.

Hence, there is more kinetic energy in the cube at Point R compared to Point Q. The cube does not reach Point P so we can ignore this point for this option. At Point S, the wooden cube comes to a stop (It’s stated in the question!) meaning there is no kinetic energy in the wooden cube. Thus, the wooden cube does have the most kinetic energy at Point R compared to the rest of the points.

This option is correct!

OPTION 3

“If the setup had 2 blocks instead of 3, the cube would have slid further than Point S.”

The current setup has 3 identical blocks holding the slope up. If there were 2 blocks instead, the slope would have been less steep, with Point P being lower than the current setup. This would mean that Point Q would also be lower. The wooden cube would thus have less gravitational potential energy as it starts at a lower height. Less gravitational potential energy will be converted to less kinetic energy as the wooden cube slides down the slope, so it would take a shorter distance for all the kinetic energy to be converted to heat and sound energy for the cube to stop. The wooden cube would thus travel a shorter distance, not even reaching Point S.

This option is wrong.

OPTION 4

“If the cube had been released at Point P instead of Point Q, the cube would have slid down slower.”

Point P is higher than Point Q. If the wooden cube is placed at Point P, it would thus have more gravitational potential energy compared to at Point Q. More gravitational potential energy will be converted to more kinetic energy when the wooden cube is released. More kinetic energy means the wooden cube can slide faster.

This option is wrong.

FINALLY, choose the correct answer.

The answer is 2.

Take note of the explanations for each option.

Common keywords written out are:

– The types of energy

– Object(s) that has that form of energy.

– Converted to

These keywords will help your child answer the science open-ended questions relating to energy conversion. 🙂

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