Mechanical Advantage — Drills · Grade 8 Science

Chapter: Work & Machines

What these drills covers

By the end of Mechanical Advantage you should be able to:

6 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: input force, output force, mechanical advantage, model, evidence, system boundary, assumption.

Problem 1

Output force is 100 N and input force is 25 N. Find actual mechanical advantage.
Answer and explanation

4

100 ÷ 25 = 4.

Problem 2

A machine has mechanical advantage 2 and input force 18 N. Find output force.
Answer and explanation

36 N

2 × 18 = 36.

Problem 3

A machine lifts a 600 N load with an effort of 150 N. What is its mechanical advantage?
Answer and explanation

4

MA = load/effort = 600/150 = 4.

Problem 4

A machine has mechanical advantage 5 and the load is 250 N. What effort is needed, in newtons?
Answer and explanation

50 N

effort = load/MA = 250/5 = 50 N.

Problem 5

A mechanical advantage less than 1 means the machine
  1. is broken
  2. multiplies distance or speed rather than force
  3. creates energy
  4. cannot work
Answer and explanation

multiplies distance or speed rather than force

Some machines trade force for speed or range of movement, as a bicycle gear can.

Problem 6

Explain why a large mechanical advantage is not always the best design choice.
Answer and explanation

A large mechanical advantage means the effort moves much further than the load, so the task takes longer and needs more room for the movement. A ramp gentle enough to need very little force may be impractically long. The right design balances the force a person can supply against the distance and time available.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the data, mechanism, or calculation that supports it.
  • Include units, conditions, or limits where relevant.

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