What is a displacement-time graph?

• Displacement-time?graphs show the?displacement?of an object from a?fixed origin?as it moves in a?straight line
• They show?displacement?(on the vertical axis) against?time?(on the horizontal axis)
• Displacement-time graphs can go?below the horizontal axis?whereas?distance-time graphs?can not
  • Distance can?not?be negative whereas displacement can be

   

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

• The?gradient?of the graph equals the?velocity?of the object
• • A?positive gradient?means the object is travelling?forwards
  • A?negative gradient?means that the object is travelling?backwards
  • The?steeper?the line, the?greater?the?speed

   

• A?straight line?shows that the object is moving at a?constant velocity
• A?curved line?shows that the object is?accelerating?or?decelerating
• A?horizontal line?shows that the object is?stationary
• If the graph?touches?the?x-axis,?then the object is?at the origin?at that time

How do I find the average speed and the average velocity of a journey?

• The average speed can?not?be?negative?as speed is a?scalar?quantity and can only take a positive value

• The average velocity is a?vector?quantity and can be?positive,?zero?or?negative

(a)? ?Calculate the velocity of the athlete during the first 2 seconds.

(b)? ? Describe the motion of the athlete between the times of 2 seconds and 5 seconds.

(c)? ?Calculate the velocity of the athlete at 10 seconds.

(d)? ?Find the total distanced travelled by the athlete during the 14 seconds.