Section 1 b) Summary

Distance-time graphs are used to show the change in distance over time: the displacement from the starting point. The velocity of an object can be determined from the gradient of one of these graphs. Negative points mean that the object is travelling in the opposite direction, and a negative gradient means the object is travelling back to the starting point.

Velocity-time graphs are used to show the change in velocity over time. The area between the line and the x-axis is used to calculate the distance travelled and the gradient is the acceleration. A negative gradient indicates deceleration and negative points mean the object is travelling backwards.

Experiments to investigate:

You could use ticker tape and a toy car on a ramp to plot a distance time graph of its movement. A mark is made on the tape at a regular interval, set by the user (e.g. every second). The distance between marks can be measured and the movement of the car plotted on a distance-time graph.

Another way of investigating the movement of an object, for example a tennis ball, is by dropping it or pushing it down a ramp and measuring the time it takes for the ball to reach a certain point after it begins moving. From this, the average speed can be calculated using the speed triangle.

Equations:

Velocity = Change in Distance / Change in Time

Acceleration = Change in Velocity / Change in Time