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Mechanisms for GCSE Design and Technology

GCSE Design and Technology, Systems and mechanisms. Usually met in years 9 to 11.

Calculate mechanical advantage, gear ratios and output speeds for levers, gears and pulleys.

What you practise

Starts with levers and builds to compound gear trains. Practice moves up a level when a round goes well and down when it does not.

Sample questions

Each sample comes with the method and the reason every wrong option is wrong. Real practice rounds are ten questions at your level.

Sample question, level 2 of 5

A driver gear with 19 teeth turns a driven gear with 57 teeth. What is the gear ratio?

  1. 38:1
  2. 4:1
  3. 5:1
  4. 3:1
  5. 1:3
Show the answer and method

Answer: D, 3:1

The method: Gear ratio = driven teeth ÷ driver teeth = 57 ÷ 19 = 3, written 3:1.

Why the other options are wrong:

  • A, 38:1: The teeth were subtracted. Divide driven by driver.
  • B, 4:1: Check the division: 57 ÷ 19 = 3.
  • C, 5:1: Check the division: 57 ÷ 19 = 3.
  • E, 1:3: Upside down: gear ratio = driven teeth ÷ driver teeth.

Sample question, level 4 of 5

A driver pulley 80 mm across turns at 320 rpm. A belt drives a pulley 40 mm across. How fast does the driven pulley turn?

  1. 960 rpm
  2. 640 rpm
  3. 320 rpm
  4. 360 rpm
  5. 160 rpm
Show the answer and method

Answer: B, 640 rpm

The method: Output speed = input speed × driver diameter ÷ driven diameter = 320 × 80 ÷ 40 = 640 rpm.

Why the other options are wrong:

  • A, 960 rpm: Output speed = input speed × driver diameter ÷ driven diameter.
  • C, 320 rpm: That is the input speed.
  • D, 360 rpm: Use the ratio of the diameters.
  • E, 160 rpm: The driven pulley is smaller, so it turns faster.

See where this fits: every GCSE option topic and Key Stage 3.

Related topics: Energy and systems.