# 7. Using Gradients to

Calculate Acceleration

# Success Criteria

Your learning has been successful if you can do the following:

Define acceleration and its units.

Calculate acceleration from speed and time measurements.

# Vocabulary

Learn these so you can communicate this concept well.

Average speed: Calculated by the total distance travelled divided by the total time taken for the journey.

Gradient / slope: How steep a line on a graph is.

Speed: How fast an object is moving.

Velocity: Similar to speed, but also tells us the direction in which an object is moving. It includes both speed and direction of motion.

Do Now:

Collect and complete this small 'Do Now'. Then glue into your SciPAD page 11. Use your commonsense when glueing - don't glue straight on-top of words!

Find some space on page 15 of your PESS1.2 SciPAD,

and answer the following questions:

What does each letter in CUTLASS stand for?

## Finding Acceleration from a Speed-Time Graph

The gradient or slope of a speed-time graph gives you the acceleration. The gradient of a speed-time graph is calculated by the change in the speed (vertical axis) divided by the change in time (horizontal axis).

Note:

Change in speed, Δv = final speed - initial speed

If the acceleration is negative, we say it is 'deceleratiing'. Decelerating can be thought of as negative acceleration.

To show and find acceleration, use a graph that shows velocity against time. This is because acceleration is the change in velocity divided by the change in time.

A car moving off from traffic lights has constant acceleration. As the seconds pass, the car increases in velocity. As it gains velocity, the car travels more road in the same time. Consider the following graphs of velocity over time.