Energy conversion: What is it and how does it work? As part of the Primary Science syllabus, students are required to understand how energy in an object/ equipment is converted from one form to another to allow the equipment to function. Most students typically understand how this is done. The tricky part usually comes when they are required to explain the reasons behind the energy conversion.
Before we dive deeper into energy conversion, we need to bear this important rule of energy in mind:
“Energy is converted from one form to another since energy can neither be created or destroyed.”
PSLE Science Questions on Energy Conversion
Kinetic & Gravitational Potential Energy
Question 1 (2020 PSLE / Q37)
Aisha tied a mass to an electric toy train as shown in Diagram 1. The train moved slowly from A to B.
Next, Aisha linked a wagon to the train as shown in Diagram 2. When she placed the same mass on the wagon, the train moved faster from A to B.
*(a) Give a reason why the train moved faster when pulling the mass on the wagon.
Note: Surface area in contact with the ground does not affect the amount of friction between the wagon and the ground.
*(b) The train moved from A to B easily but moved up the slope slowly.
Explain why the train moved up the slope slowly. [1]
Note: Not advisable to use “the train has to overcome gravitational force”. Better to explain as “the motion of train is going against the “gravitational force”. The amount of gravitational force acting on the train does not change with its height; only gravitational potential energy increases with increasing height.
Kinetic & Gravitational Potential Energy
Question 1 (2020 PSLE / Q37) continue…
The train and wagon were linked by plastic rings as shown in the image.
When the wagon was on the slope, it broke loose from the train and rolled downwards as shown in the diagram below. The plastic rings used for linking the wagon to the train were not broken.
(c) Explain why the wagon broken loose from the train on the slope without breaking the plastic rings. [1]
Note: Friction results in converting kinetic energy into heat energy, allowing the plastic ring of the wagon to gain heat and expand, hence becoming bigger.
Energy Conversion: Kinetic & Gravitational Potential Energy
Question 2 (2019 PSLE / Q37)
Zhi Ming set up the apparatus below to investigate how his toy car can move on its own along the plastic track from A down to B, up to C before leaving at D. C is at a fixed height above B.
*(a) When Zhiming released the car at A, it moved past B but was not able to reach C. Explain why. [1]
*(b) Without using different apparatus and additional materials, suggest two different ways to help the car reach C in this investigation. Explain your answer. [2]
(c) State the main form(s) of energy that the car will have at C. [1]
Note: The toy car is moving at C and so it still has kinetic energy in addition to the potential energy possessed by the toy car when at a height.
Energy Conversion: Chemical Potential Energy, Electrical Energy & Kinetic Energy
Question 3 (2018 PSLE / Q35)
Peter has a toy train that runs on batteries. He placed plates of food on the train as shown below.
(a) When he switched on the toy train, it moved along the track.
Fill in the boxes below to show the energy conversion as the train is moving. [2]
*(b) Peter did not change the batteries. Give a reason why the train moved faster as the food was removed. [1]
*(c) Peter placed a wooden block under the track at point H.
Explain why the train moved more slowly as it moved from G to H. [1]
