Physics

The big ideas of physics

Physics is the study of how the world works, from a falling ball to the flow of electricity. A few big ideas run through it all. Forces make things speed up, slow down or change direction. Energy is transferred from one store to another but is never created or destroyed. Electricity is the flow of charge that powers our homes. Waves carry energy from place to place, whether as light or sound. This unit gives you the overview a Single Award scientist needs: the main ideas, the quantities and their units, and how to work out a simple result such as a speed.

The words of physics

Learn these terms before the ideas are described. They name the main quantities of physics.

Match each quantity to its unit

Renewable against non-renewable energy

The energy that powers our lives comes from different sources, and physics sorts them into two groups by whether they run out.

Which quantity is in newtons?

Which physical quantity is measured in newtons?

• Force
• Energy
• Current
• Frequency

Energy is never lost

One idea holds much of physics together: the conservation of energy. Energy is never made from nothing and never simply vanishes; it only moves from one store to another. When a ball falls, the energy in its raised position is transferred to movement energy. When a device runs, electrical energy is transferred to light, sound, heat or movement. Some energy usually spreads out as wasted heat, which is why nothing is perfectly efficient. So when you explain any device or event, track where the energy starts and where it ends up. Follow the energy, and much of physics makes sense.

Pick the true physics facts

Select every true statement about physics.

• Forces can change the speed of an object
• Energy is transferred, never created or destroyed
• Waves carry energy without carrying matter
• Energy can be made from nothing
• Forces have no effect on how things move

Order how to find speed

Put the steps for working out the speed of a moving object in the correct order.

• Measure the distance travelled
• Measure the time taken
• Divide the distance by the time
• Give the answer in metres per second
• Check the answer is sensible

Complete the physics unit facts

A push or pull that changes motion is a _____. It is measured in _____. Energy is never created or destroyed, only _____. Speed is worked out by dividing distance by _____.

One car, one speed

Suppose a car travels one hundred metres along a straight road and it takes five seconds. To find its speed you divide the distance by the time. One hundred metres divided by five seconds gives twenty, so the car is moving at twenty metres per second. Notice the method: the distance goes on top, the time on the bottom, and the unit of the answer, metres per second, comes straight from the units you divided. If the car covered the same distance in ten seconds it would be moving at only ten metres per second, half as fast. Getting the quantities and their units right is what makes a physics calculation trustworthy.

Tap the renewable sources

Tap the TWO energy sources that are renewable.

• wind
• solar
• coal
• gas

Work out the car speed

A car travels 100 metres in 5 seconds. What is its speed in metres per second? Divide the distance by the time.

Apply the physics ideas

Read each situation and choose the best answer.

• A device turns electrical energy into light and some heat. Which idea explains why not all of it becomes light?
• A source of energy that will not run out and depends on the sun is being chosen. What kind is it?
• A runner covers 40 metres in 8 seconds. What is their speed?

Build a physics idea

Choose the word for each gap to complete one clear point about physics.

Explain the big ideas of physics

A friend thinks physics is just a jumble of unrelated facts. Using what you have learned, explain the big ideas that hold physics together.

• Explain what a force does and how it is measured
• Explain the conservation of energy
• Explain how to work out a speed
• Explain the difference between renewable and non-renewable energy