Physics · High School (11–12)

Why does a book on a table stay still, a hockey puck slide on and on, and a car skid on a wet road? Three laws, written by Newton more than three hundred years ago, answer all of these and many more. In this chapter we learn the three laws, we draw the forces on a body, we solve problems with pulleys, slopes and friction, and we find the force that keeps a car on a bend. Python solves the equations and draws the graphs.

A roller coaster climbs slowly, and then it races down. A bat hits a ball, and the ball flies away. A motor lifts a load in one minute, and a bigger motor does it in ten seconds. In each case, energy goes from one place or form to another. In this chapter we learn what work is, how it changes the motion of a body, how energy is stored and kept, how fast work is done, and what happens in a collision. Python adds up the work, draws the energy graphs and solves the collisions.

A diver tucks in the air and spins fast, and then opens out and enters the water. A ladder leans on a wall and does not slip. A cylinder rolls down a slope faster than a ring. Up to now, we treated every body as a point. Real bodies have a size and a shape, and they can turn. In this chapter we find the one point where a body or a system behaves like a single particle, we learn what torque, moment of inertia and angular momentum are, and we use them to study spinning, balancing and rolling. Python adds up the masses, solves the equations of balance and races the rolling bodies.

An apple falls, the Moon goes round the Earth, and the Earth goes round the Sun. Newton saw that one law of gravitation explains all three. In this chapter we start from the laws that Kepler found in the observations of the planets, we write the law of gravitation, we find how gravity changes above and below the surface, we find the energy that is needed to leave the Earth, and we study satellites, from the Moon to a weather satellite, and the weightlessness of an astronaut. Python solves the orbits and the energy.

A steel cable holds a lift, a bridge bends a little under a lorry, and a rubber band snaps back. A solid changes its shape when we push, pull or twist it, and it comes back when we let it go. In this chapter we measure how much a solid changes, with stress and strain, we find the three moduli of elasticity that describe steel, copper or rubber, we find the energy that is stored in a stretched wire, and we use all this to choose the rope of a crane and the beam of a bridge. Python fits the moduli and designs the beams.

A diver feels the water press on the ears, a ship of steel floats, a plane stays in the air and a drop of water holds its shape on a leaf. Liquids and gases are called fluids, because they flow. In this chapter we find the pressure inside a fluid and the force of buoyancy, we study how a fluid flows, from a pipe to the wing of a plane, and we meet two properties that belong to the surface and the layers of a fluid, the surface tension and the viscosity. Python finds the pressure, the speed of the flow and the rise of water in a thin tube.

A railway track has small gaps, a cup of tea cools in the room, ice at 0 degrees takes a lot of heat to melt, and the Sun warms the Earth through empty space. In this chapter we measure temperature and learn what it means, we find the law of the ideal gas, we find how much solids and liquids expand, we measure heat with the specific heat and the latent heat, and we study the three ways in which heat travels: conduction, convection and radiation. Python solves the mixing of hot and cold water, draws the cooling curve and finds the temperature of the Sun.

A bicycle pump becomes warm when you use it, a refrigerator cools its inside and warms the kitchen, and no engine turns all the heat of its fuel into work. In this chapter we find how heat and work change the energy of a gas, which is the first law, we follow a gas through the four basic processes on a pressure-volume graph, and we learn why the second law and entropy set a limit on every engine. Python computes the work from the area under a curve, compares isothermal and adiabatic changes and finds the efficiency of the Carnot engine.

A ripple on a pond, a note on a guitar, a voice across a room. All of them are waves. In this chapter you learn how fast a wave goes and what happens when two waves meet. You learn why a string or a pipe can play only certain notes. You also do an experiment with a tuning fork and a tube of air to measure the speed of sound. Python draws the waves for you.

A battery, a wire and a bulb. A few rules tell you what every part of a circuit does. In this chapter you learn how current, voltage and resistance fit together. You join resistors one after another (in series) and side by side (in parallel). You also solve circuits that have more than one battery. Python checks your work.

Light is a wave. But light also comes in small packets of energy. And an atom can have only certain amounts of energy. These two ideas changed physics. In this chapter you follow the experiments behind them. First, light that knocks electrons out of a metal. Then, why hydrogen gives out only a few colours. Every calculation is also done in Python.