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Grade 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.

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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 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 meters? Answer with a number.

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

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

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

  4. 4.A cyclist covers 300 m of path in 60 s. What is her average speed, in m/s? Answer with a number.

  5. 5.A stone is dropped from a height. Put its speeds in order, starting from 0 m/s, at the instant it is released.

    • 29.4 m/s, after three seconds
    • 19.6 m/s, after two seconds
    • 0 m/s, at the instant it is released
    • 9.8 m/s, one second later

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

  7. 7.A train speeds up from 8 m/s to 20 m/s in 6 s. What is the magnitude of its average acceleration, in m/s²? Answer with a number.

  8. 8.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

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

  1. 1. 0
  2. 2. c) Its direction keeps changing while its magnitude stays fixed
  3. 3. a) Uniform motion in a straight line
  4. 4. 5
  5. 5. 1. 0 m/s, at the instant it is released 2. 9.8 m/s, one second later 3. 19.6 m/s, after two seconds 4. 29.4 m/s, after three seconds
  6. 6. 20
  7. 7. 2
  8. 8. 3 — The stretch from O to B