What is a velocity-time graph?

• Velocity- time?graphs show the?velocity?of an object as it moves in a?straight line
• They show?velocity?(on the vertical axis) against?time?(on the horizontal axis)
• Velocity-time graphs can go?below the horizontal axis?whereas?speed-time graphs?can not

What are the key features of a velocity-time graph?

• The?gradient?of the graph equals the?acceleration??of an object
• A?straight line?shows that the object is?accelerating?at a?constant rate
• A?horizontal?line shows that the object is moving at a?constant velocity
• The?area?between graph and the x-axis tells us the?change in?displacement?of the object
  • Graph?above?the x-axis means the object is moving?forwards
  • Graph?below?the x-axis means the object is moving?backwards

   

• The?total displacement?of the object from its starting point is the sum of the?areas above?the x-axis?minus?the sum of the?areas below?the x-axis
• The?total distance travelled?by the object is the sum of?all?the?areas
• If the graph?touches?the?x-axis?then the object is?stationary?at that time
• If the graph is?above?the?x-axis?then the object has positive velocity and is?travelling forwards
• If the graph is?below?the?x-axis?then the object has negative velocity and is?travelling backwards

(a) Calculate the acceleration of the bird at 20 seconds.

(b) Calculate the distance travelled in the first 28 seconds.

(c) Calculate the displacement of the bird from its starting point after 60 seconds.