Motion

The distance-time graph for any object that is stationary is a horizontal line.

The distance-time graph for any object that is moving at a constant speed is a straight line that slopes upwards.

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

Speed (m/s) = Distance Travelled (m) ÷ Time Taken (s)

• A vector is a physical quantity that has a direction as well as a magnitude.
• A scalar is a physical quantity that has a magnitude only and does not have a direction.

Velocity is speed in a given direction.

Displacement is distance in a given direction. Acceleration is change of velocoity per second. The unit of acceleration is the metre per second squared (m/s²)

Acceleration = change of velocity ÷ time taken.

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

• If a velocity-time graph is a horizontal line, the acceleration is 0.
• The gradient of the line on a velocity-time graph represents acceleration.
• The area under the line on a velocity-line graph represents distance travelled.

The speed of an object is given by the gradient of 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 distance travelled by an object is given by the area under the line of its velocity-time graph.

Gradient of a line/triangle = Height of line/triangle ÷ Base of line/triangle

TIP: If you are drawing a straight line graph, always use a ruler (it says so in the book XD)

TIP: Be careful with units, especially the unit of acceleration. The unit is m/s² - that is the change in speed, measured in m/s, that occurs every second.