- A-Level Physics

# Motion, Momentum & Impulse

Everything in the universe is in motion, and there are basic laws of mechanics that govern this.

Velocity is the rate of change of an object's position, and therefore has direction. **This makes it a vector quantity, unlike speed which is scalar (magnitude but no direction).**

velocity = distance / time

**The units of velocity are m/s**

Acceleration is the rate of change of velocity, and so is the mathematical derivative of this.

acceleration = change in velocity / change in time

**The units of acceleration are m/s²**

## Motion Graphs

We can plot motion on two main types of graph - it is important to know the properties of each.

### Displacement-Time Graphs

The Gradient is the velocity - draw a tangent to find the instantaneous velocity

Horizontal line represents zero velocity

### Velocity-Time Graphs

The Gradient is the acceleration

The Area beneath the graph is the displacement

## Linear Motion

When acceleration is constant (e.g. free fall when we ignore air resistance), we can use SUVAT equations to work out the variables:

Linear motion can be investigated with trolley cars, air gliders, ticker tape, light gates, data loggers and motion capture.