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Class 9 Science — Distance, displacement, speed and velocity

Separate distance from displacement and speed from velocity, work out average speed, average velocity and average acceleration, and say what stays fixed in uniform circular motion.

Name: ________________________

Before you start

Slide along the track. The starting line sits at 0 and the far end at 100.

020406080100

Positions to the right of the starting line count as positive. A runner who goes out to 100 and comes back to 40 has covered a long path but ended up 40 from where she started.

  1. 1.A cyclist rides round a circular track at a steady 8 m/s. What is happening to her velocity?

    • a) Its direction keeps changing while its magnitude stays fixed
    • b) It falls to zero each time she completes a lap
    • c) Its magnitude keeps changing while its direction stays fixed
    • d) Both its direction and its magnitude stay fixed

  2. 2.A bus covers 15 m in the first second, 15 m in the second and 15 m in the third. What does the chapter call this motion?

    • a) Uniform motion in a straight line
    • b) Non-uniform motion in a straight line
    • c) Uniform circular motion
    • d) Motion with constant acceleration

  3. 3.An athlete runs along the track from O out to A, then turns and comes back as far as B. Tap the bar whose length is the magnitude of her displacement.

    Write the number of the part.

    123

  4. 4.A lorry is doing 72 km/h. What is that in m/s? Answer with a number.

  5. 5.A child on a merry-go-round rides exactly once round the circle and stops where she got on. What is the magnitude of her displacement, in metres? Answer with a number.

  6. 6.Match each quantity to its SI unit.

    • Displacement
    • Average velocity
    • Average acceleration
    • metre
    • metre per second squared
    • metre per second

  7. 7.Sort each quantity by whether stating it takes a direction as well as a number.

    Groups: Number on its own · Number and a direction

    • Average speed
    • Total distance travelled
    • Average velocity
    • Displacement
    • Average acceleration

  8. 8.A runner starts at 0, runs out to the 100 m mark, then turns and runs back 60 m. Which mark is she standing on at the end?

    Mark the line with an X.

    020406080100

Answer key — Class 9 Science — Distance, displacement, speed and velocity

  1. 1. a) Its direction keeps changing while its magnitude stays fixed
  2. 2. a) Uniform motion in a straight line
  3. 3. 3 — The stretch from O to B
  4. 4. 20
  5. 5. 0
  6. 6. Displacement → metre; Average velocity → metre per second; Average acceleration → metre per second squared
  7. 7. Total distance travelled → Number on its own; Average speed → Number on its own; Displacement → Number and a direction; Average velocity → Number and a direction; Average acceleration → Number and a direction
  8. 8. 40