- How can we describe the way things move?
Even when things are moving in a straight line, describing their movement is not easy. They can move with different speeds and can also change their speed and/or direction (accelerate). Graphs can help us to describe the movement of the body. These may be distance-time graphs or velocity-time graphs.
- How do we make things speed up or slow down?
To change the speed of a body an unbalanced force must act on it.
- What happens to the movement energy when things speed up or slow down?
When a body speeds up or slows down, its kinetic energy increases or decreases. The forces which cause the change in speed do so by transferring energy to, or from, the body.
- What is momentum?
The faster a body is moving the more kinetic energy it has. It also has momentum. When working out what happens to bodies as a result of explosions or collisions it is more useful to think in terms of momentum than in terms of energy.
- What does the current through an electrical circuit depend on?
The size of the current in a circuit depends on how hard the supply tries to push charge through the circuit and how hard the circuit resists having charge pushed through it.
- What is mains electricity and how can it be used safely?
Mains electricity is useful but can be very dangerous. It is important to know how to use it safely.
- Why do we need to know the power of electrical appliances?
Electrical appliances transform energy. The power of an electrical appliance is the rate at which it transforms energy. Most appliances have their power and the potential difference of the supply they need printed on them. From this we calculate their current and the fuse they need.
- What happens to radioactive substances when they decay?
To understand what happens to radioactive substances when they decay we need to understand the structure of the atoms from which they are made.
- What are nuclear fission and nuclear fusion?
Nuclear fission is the splitting of atomic nuclei and is used in nuclear reactors as a source of heat energy which can be transformed to electrical energy. Nuclear fusion is the joining together of atomic nuclei and is the process by which energy is released in stars.