## What to expect

Mechanics is the study of the interactions between physical bodies and their consequent motion.

After studying this topic, you should be able to:

- Define the quantities used to describe motion (displacement, velocity, acceleration).
- Derive a set of equations that give the relationship between the displacement, velocity, acceleration and time when the acceleration is constant.
- Solve problems involving constant acceleration in 1 and 2-dimensions.
- Understand the effects of forces .
- Relate unbalanced forces to motion.
- Consider energy and the capabilities that this gives to bodies.
- Define power and efficiency.
- Learn about types of collision in terms of conservation of momentum

## Key questions

#### What are the types of motion graphs?

Motion graphs come in two main formats: displacement vs time (gradient is velocity) and velocity vs time (gradient is acceleration and area is displacement). Find out more.

#### How do you use the equations of motion?

To solve problems using the equations of motion, annotate the question with the three quantities that are provided (e.g. *u*, *a* and *t*) then select the equation that includes these and the desired quantity (e.g. *v*). Rearrange, substitute and solve. Find out more.

#### What are examples of forces?

Normal reaction, weight, tension, friction and drag are some examples of forces. Find out more.

#### What are Newton's 1^{st}, 2^{nd} and 3^{rd} laws?

Newton's 1st law states that an object will remain at rest or at constant velocity unless acted upon by a resultant force. Find out more.

Newton's 2nd law states that the rate of change of a momentum of a body is proportional to the resultant force and is in the same direction as the force. Find out more.

Newton's 3rd law states that if body A exerts a force on body B, body B exerts an equal and opposite force on body A. Find out more.

#### How do we define power in physics?

Power is defined as the rate at which work is done. Find out more.

#### What happens to momentum when cars collide?

Momentum is a quantity that is *conserved*. This means that the total amount is constant throughout an interaction, such as a collision, provided that there are no external forces acting. Find out more.

### Kinematics

Kinematics is the study of moving objects.

### Forces

Every new movement, direction, squash or stretchÂ requires a force.

### Work and energy

Work done and energy changed are equivalent.