Speed + Velocity + Distance-Time Graphs

What is speed?

The distance travelled per unit time.

What is the SI unit of speed?

Metres per second (m/s).

What is average speed?

Total distance travelled divided by total time taken.

What is a typical walking speed?

Approximately 1.5 m/s.

What is a typical running speed?

Approximately 3 m/s.

What is a typical cycling speed?

Approximately 6 m/s.

What is the approximate speed of sound in air?

330 m/s.

What is velocity?

Speed in a given direction.

Can an object have constant speed but changing velocity?

Yes, if its direction changes.

Why does an object travelling in a circle at constant speed have changing velocity?

Velocity is a vector, and its direction continually changes.

Why must a resultant force act on an object moving in a circle?

Its velocity is changing, so it is accelerating and requires a resultant force.

In which direction does the resultant force act during uniform circular motion?

Towards the centre of the circle.

What does the gradient of a distance–time graph represent?

Speed.

What does a horizontal line on a distance–time graph mean?

The object is stationary.

What does a straight line with a constant positive gradient mean?

The object is moving at constant speed.

What does a steeper gradient mean?

A greater speed.

What does a curved distance–time graph mean?

The object's speed is changing.

How can instantaneous speed be determined from a curved distance–time graph?

Draw a tangent to the curve at the required time and determine its gradient.