Physics · High School (9–10)

You push a heavy cart and you get tired. You sit and read for an hour, and you are tired too. Which one is work in physics? In this chapter we learn what work is and how we measure it. Then we meet energy, the stored ability to do work, and we follow it as it changes from one form to another. We end with power and the unit that appears on an electricity bill. Python helps us with the calculations.

You hear a drum from far away, and you see the lightning before you hear the thunder. How does a sound reach your ear? In this chapter we find out what sound is, why it needs air or some other material to travel, and how fast it goes. Then we describe a sound by its frequency and amplitude, and we learn why a sound can be loud or soft, and high or low. We end with echoes, the human ear and the uses of ultrasound. Python helps us with the calculations.

You see your face in a spoon, and a straw in a glass of water looks broken. Light does both of these things, and it follows simple rules. In this chapter we find the rules of reflection and refraction. We use them to understand mirrors and lenses, to draw where an image forms, and to calculate its place and size with a formula. Python helps us draw and calculate.

You read this page because an image forms on a screen at the back of your eye. A rainbow appears after rain, the sky is blue at noon, and the Sun is red at sunset. Light explains all of these. In this chapter we study how the eye works and how spectacles correct it, how a prism splits white light into colours, and why the sky has the colours that we see. Python helps us calculate and draw.

You switch on a light, and the room is bright at once. A heater warms the room, and a phone charger fills a battery. All of them use electric current. In this chapter we find out what current is, what pushes it through a wire, and what makes a wire resist it. We join resistors in series and in parallel, we measure the heat that a current makes, and we learn how to find the power and the cost of an appliance. Python helps us calculate and draw.

A compass needle moves when you bring a wire with a current near it. A crane lifts a car with a magnet that you can switch off. A fan turns, and a power station makes electricity, with the same two ideas: a current has a magnetic field, and a magnet and a coil can make a current. In this chapter we study the field of a current, the force that a field makes on a current, the electric motor, the generator, and the safe wiring of a house. Python helps us calculate and draw.