Year 7 Science · Unit 3 · Lesson 13
Challenge Worksheet
Learning Goals
What if…?
Scenario
Imagine an inventor claims to have built a special wheel that, once you give it one push, keeps spinning forever and even speeds up on its own, with no one ever pushing it again. The inventor says it makes free energy out of nothing. You know from this lesson that forces transfer energy, that friction turns movement energy into heat, and that energy is always conserved.
Using what you know about force, energy transfer, friction and the conservation of energy, explain why the inventor's claim cannot be true. Use scientific terms (force, work, kinetic energy, friction, conserved) and give at least two clear reasons.
1. A roller coaster car is released at the top of the first hill with no engine. It races down, climbs the next hill, races down again, and so on, but each hill it reaches is a little lower than the one before. Explain this pattern by tracing the energy changes and naming where energy ends up. Use the word friction in your answer.
2. Two identical balls are lifted onto a shelf. Ball A is lifted twice as high as Ball B. Both are then released and fall. Predict which ball is moving faster just before it hits the floor, and explain your answer using the idea of stored energy changing into movement energy.
Wrap Up
In one sentence, what was the main idea of this lesson?