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)
Velocity & Acceleration
- 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.