The gradient of a displacement-time graph gives the velocity
Motion & Kinematics - OCR A-Level Physics
- The gradientThe rate of change of one variable with respect to another; the slope of a graph at a point. of a displacementThe distance moved in a particular direction from a starting point. A vector quantity. Measured in metres (m).-time graph gives the velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.
- A straight line indicates constant velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹.
- A horizontal line indicates the object is stationaryNot moving; the object has zero velocity. ($velocityThe rate of change of displacement. A vector quantity. Measured in m s⁻¹. = 0)$
- A curve indicates changing velocity (the object is accelerating or decelerating)
- A negative gradient indicates motion in the opposite direction to the positive convention
- The instantaneous velocityThe velocity at a specific moment in time, given by the gradient of a displacement–time graph at that point. at a point on a curve is found by drawing a tangent and calculating its gradient
Examiner Tips and Tricks
- When asked for instantaneous velocity from a curved s-t graph, draw the tangent at the specified time and show your triangle clearly.
- Examiners award marks for the method even if the tangent is slightly off.