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Grade 8 · Science · Unit 16 of 16

Gears, Pulleys & Efficiency

Speed ratios, force ratios and why friction matters

What your child practises

How gears trade speed for force, how pulleys and screws are used, how to calculate efficiency, and how designers weigh efficiency against effects on people and the environment.

Nunavut Curriculum approved guide: Nunavut adaptation of Alberta Science 7–9 (2003), Unit D: Mechanical Systems · gears, belts and pulleys that transmit force and motion, speed and force ratios, efficiency, and how mechanical devices have changed over time

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    A bicycle chain connects two gears. Which system is this?

    • a chain drive, which transmits motion between shafts
    • an electric circuit
    • a hydraulic lift
    • a pneumatic drill

  2. Question 2

    A small gear drives a large gear. What happens to the force?

    • The force increases and the speed decreases.
    • Both stay exactly the same.
    • Both increase.
    • The force decreases and the speed increases.

  3. Question 3

    What does a grain auger use to move grain up a tube?

    • a mirror
    • a magnet
    • a rotating screw
    • a lens

  4. Question 4

    A fixed single pulley mainly…

    • halves the distance
    • removes friction
    • doubles the force
    • changes the direction of the force

  5. Question 5

    Why should a mechanical device be evaluated for its impact on the environment as well as its efficiency?

    • A very efficient device might still cause pollution or use up resources.
    • The environment is not affected by machines.
    • Impact cannot be measured.
    • Efficiency is the only thing that matters.

  6. Question 6

    A driver gear with 10 teeth turns a driven gear with 40 teeth. The driver makes 24 full turns. How many full turns does the driven gear make?

    answer box

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