Experiment Design
You test how the height of a ramp affects the speed of a toy car. Name one variable you would need to keep controlled.
The type of car, the surface of the ramp, or the ramp material.
100: What type of potential energy is stored in a stretched rubber band?
Elastic potential energy
What is the formula for calculating efficiency?
Efficiency = (Useful energy output ÷ Total energy input) × 100
What law states that energy cannot be created or destroyed?
Law of Conservation of Energy
What is a hypothesis?
A testable prediction based on prior knowledge or observations.
A group measures how long it takes a kettle to boil but uses different amounts of water each time. What’s the flaw?
The volume of water isn’t controlled, so boiling times can’t be compared fairly.
A ball held at the top of a hill has what kind of potential energy?
Gravitational potential energy
A light bulb uses 100 J of energy but only produces 20 J of light. What is its efficiency?
20%
Why does a basketball eventually stop bouncing, even though no one touches it?
Because its kinetic energy is gradually transformed into heat and sound with each bounce until it has no useful energy left to keep moving.
What is the difference between an independent and a dependent variable?
Independent = what you change
Dependent = what you measure.
A student tests how temperature affects how quickly sugar dissolves, but they stir some cups faster than others. What’s the flaw?
Stirring speed isn’t controlled; differences in dissolving could be due to stirring, not temperature.
Two tennis balls are placed at the same height, but one is twice as heavy. Which ball has more gravitational potential energy, and why?
The heavier tennis ball, because gravitational potential energy depends on both mass and height.
If a motor is 80% efficient, what happens to the other 20% of the energy?
It is wasted, usually as heat and sound energy.
Solar panels convert sunlight into electricity. What type of energy conversion is this?
Light energy → Electrical energy.
Why do scientists use controlled variables in experiments?
To ensure a fair test by keeping other factors the same.
A group is testing how slingshot tension affects projectile distance. If one group member pulls back further than others, what kind of error could this cause?
An uncontrolled variable causing inconsistent results and reducing reliability.
A diver stands on a 10 m platform and another on a 5 m platform. Compare their gravitational potential energies if their masses are the same.
The diver on the 10 m platform has twice as much gravitational potential energy, since height has doubled.
400 (new): A diver stands on a 10 m platform and another on a 5 m platform. Compare their gravitational potential energies if their masses are the same.
The diver on the 10 m platform has twice as much gravitational potential energy, since height has doubled.
A phone battery runs down quickly when lots of apps are open. What does this show about energy use?
More processes use more electrical energy, and some of it is wasted as heat.
In an energy investigation, you measure the bounce height of a ball dropped from different heights. What is the independent variable?
The drop height.
A class tests how ramp angle affects speed, but they only do one trial at each angle. What’s the flaw?
Lack of repeats means no reliability check; results could be due to chance.
A rollercoaster cart has 800 J of potential energy at the top of a hill. At the bottom, it has 750 J of kinetic energy. What happened to the missing 50 J?
It was transformed into heat and sound due to friction and air resistance.
A device takes in 500 J of energy and outputs 350 J as useful work. Calculate its efficiency as a percentage.
(350 ÷ 500) × 100 = 70%
500: A scientist says, “No energy conversion is 100% efficient.” Explain why this is true, giving an example.
Because some energy is always transformed into less useful forms (usually heat or sound). Example: a car engine loses energy as heat, not just motion.
A group investigates how the length of a bungee cord affects how far a weight falls. They only test one weight, on a windy day, and conclude that “longer cords are always more dangerous.” What are the flaws in this experiment and conclusion?
Flaws include: not testing with different weights, failing to control environmental factors (wind), not repeating trials, and making an overgeneralised conclusion.