Changing speed

Question 1

What is change of speed per unit time on a speed-time graph called

Answer 1

Acceleration

Question 2

What happens when the speed increases or decreases in a speed-time graph.

Answer 2

• When the speed increases, the object accelerates.
• When the speed decreases, the object deaccelerates.

Question 3

What is the area of a speed-time graph equal to?

Answer 3

The distance travelled.

Question 4

Formula for Acceleration

Answer 4

Acceleration = change in speed or velocity/time taken

Question 5

Unit for Acceleration

Answer 5

m/s²

Question 6

Negative acceleration is

Answer 6

Deacceleration

Question 7

What is velocity?

Answer 7

Velocity is a vector - it has both size (speed) and direction.

Question 8

When two cars are moving past each other, their relative velocity is:

Answer 8

• The sum of their individual velocities if they are going in opposite directions
• The difference of their individual velocities if they are going in the same direction.

Question 9

Circular motion

Answer 9

• A vehicle may go around a roundabout at a constant speed but it is accelerating. This is because its direction of travel is changing; it’s not going in a straight line. The driver needs to apply a force towards the centre of the roundabout to change direction. This gives the vehicle an acceleration directed towards the centre of the roundabout.
• Any object moving along a circular path moves at a tangent to the circle, or arc of a circle.