P9 Motion

Speed and Distance-Time Graphs

If an object is moving at a constant speed, the distance-time graph is a straight line that slopes upwards

The gradient of a distance-time graph for an object represents the object's speed

If an object is stationary, the distance-time graph is a horizontal line

Velocity = Speed / Time

Velocity and Acceleration

A scalar is a physical quantity that has a magnitude only and does not have a direction

Acceleration = Change in velocity / time

A vector is a physical quantity that has a direction as well as a magnitude

Deceleration is the change of velocity per second when an object slows down

Velocity is speed in a given direction

Velocity-Time Graphs

If a velocity-time graph is a horizontal line, the acceleration is zero

A positive gradient on a velocity-time graph represents positive acceleration, a negative gradient represents deceleration

The gradient of the line on a velocity-time graph represents acceleration

A motion sensory linked to a computer can be used to measure velocity changes

The area under the line on a velocity-time graph represents distance travelled

Analyzing Motion Graphs

The distance traveled by an object is given by the area under the line on its velocity-time graph

The speed at any instant in time, of an object moving at changing speed is given by the gradient of the tangent to the line on its distance-time graph

The acceleration of an object is given by the gradient of the line on its velocity-time graph

The speed of an object moving at constant speed is give by the gradient of the line on its distance-time graph