2.9 Linear Motion

• Distance, displacement, speed, velocity and acceleration
• Average speed and average velocity
• Distance-time graphs
• Velocity-time graphs
• Equations of uniformly accelerated motion

• distinguish distance from displacement and speed from velocity
• calculate average speed and velocity
• interpret distance-time and velocity-time graphs
• apply the equations of uniformly accelerated motion

“What can a graph tell you about a journey that a number cannot?”

The titles are open to everyone. Reading a lesson needs an account — sign in or create one.

1. Describing motion
   40 min · 2 practice tasks · quiz
   The quantities that describe a journey, and the difference a direction makes.
2. Motion graphs and equations
   40 min · 2 practice tasks · quiz
   Reading a journey from its graph, and the four equations of uniform acceleration.
3. Units of speed
   40 min · 1 practice tasks · quiz
   Change kilometres per hour to metres per second and back, and keep every quantity in one system before substituting.
4. Displacement on a line
   40 min · 1 practice tasks · quiz
   Take one direction as positive, then add signed steps to get net displacement.
5. Average and instantaneous speed
   40 min · 1 practice tasks · quiz
   Average speed is for an interval; instantaneous speed is the value at one moment, read as a gradient.
6. Acceleration and retardation
   40 min · 1 practice tasks · quiz
   Acceleration is the rate of change of velocity, with a sign; retardation is negative acceleration when slowing down.
7. Drawing displacement-time graphs
   40 min · 1 practice tasks · quiz
   Plot a displacement-time graph from a table or a story, using straight lines for uniform velocity.
8. Interpreting displacement-time graphs
   40 min · 1 practice tasks · quiz
   Read velocity from the gradient, rest from a horizontal, and a meeting from an intersection.
9. Drawing velocity-time graphs
   40 min · 1 practice tasks · quiz
   Plot velocity against time from a table or a story of uniform acceleration, rest and braking.
10. Area under a velocity-time graph
    40 min · 1 practice tasks · quiz
    The area between a velocity-time graph and the time axis is the displacement; split it into triangles and rectangles.
11. Gradient of a velocity-time graph
    40 min · 1 practice tasks · quiz
    The gradient of a velocity-time graph is acceleration; a negative gradient is retardation.
12. Choosing equations of motion
    40 min · 1 practice tasks · quiz
    List the knowns, spot the missing symbol, and pick the uniform-acceleration equation that omits it.
13. Relative speed in the same direction
    40 min · 1 practice tasks · quiz
    When two bodies move the same way, the relative speed is the difference of their speeds.
14. Relative speed in opposite directions
    40 min · 1 practice tasks · quiz
    When two bodies move towards or away from each other, the relative speed is the sum of their speeds.
15. Journeys, races and road safety
    40 min · 1 practice tasks · quiz
    Combine graphs, equations and relative speed on Kenyan journeys, school races and stopping distances.