Speed-Time Graphs

Speed-Time Graphsvideo

Speed-time graphs

How do I use a speed-time graph?

• Kinematics is the study of motion of objects

  • It looks at how an object moves over time

• Speed-time graphs show the speed of an object at different times

  • Speed is on the vertical axis

  • Time is on the horizontal axis 

• The gradient of the graph is the acceleration

  • $\mathrm{Acceleration} = \frac{\mathrm{speed}}{\mathrm{time}} = \frac{\mathrm{rise}}{\mathrm{run}}$

• A positive gradient shows positive acceleration (speeding up)

• A negative gradient shows negative acceleration, (slowing down)

  • This is also called deceleration

• Horizontal lines indicate moving at a constant speed

  • The object is neither speeding up or slowing down

  • If the constant speed is zero, then it is at rest

• A straight line shows constant acceleration

• A curve shows changing acceleration

  • To find the acceleration at a particular point on the graph

    • draw a tangent to the graph at this point and find its gradient

• The distance covered by the object is the area under the graph

  • Split the area into simple shapes, e.g. rectangles and triangles

  • Find the area of each shape and add them together