Velocity-time graphs

• The velocity-time graph shows how velocity changed with time
• Velocity-time graph


  • Shows how velocity changes with time
  • Looks different from distance-time graph
• Calculating acceleration from a velocity-time graph


  1. Step 1: Write down what you know

  2. Step 2: Write down the equation

  3. Step 3: Put the numbers into the equation and solve
• Horizontal line on a velocity-time graph

  Means constant speed
• Diagonal line sloping up


  Shows constant acceleration
• Diagonal line sloping down

  Shows constant deceleration
• Objects represented in velocity-time graphs

  • Object P (constant velocity)
  • Object Q (constant acceleration)
  • Object R (constant deceleration)
  • Object S (accelerates and then decelerates)
• A velocity-time graph can tell you how the velocity of an object is changing
• The change in velocity is calculated as final velocity minus initial velocity
• Acceleration is calculated as change in velocity divided by time taken
• The velocity of the runner is 0 m/s when resting
• The runner's velocity changes from running to walking to resting
• Calculate the acceleration between C and D in Figure 3
• The average acceleration of the car over the whole 50 seconds can be calculated
• A velocity-time graph is a useful way of describing how an object is moving
• If the object is moving at a constant velocity the line is horizontal
• If the object has a constant acceleration the line is diagonal