Levers, Ramps & Pulleys — Drills · Grade 8 Science
Chapter: Work & MachinesWhat these drills covers
By the end of Levers, Ramps & Pulleys you should be able to:
- I can describe how a simple machine changes force or its direction.
- I can explain the trade-off between force and distance in an ideal machine.
6 questions, written answer, multiple choice and numeric, each with a worked explanation.
Vocabulary used: simple machine, fulcrum, ideal machine, model, evidence, system boundary, assumption.
Problem 1
Answer and explanation
A seesaw pivots around its central support.
Problem 2
Answer and explanation
The same work is transferred, so smaller input force acts through a greater input distance.
Problem 3
- reducing the work needed
- changing the size or direction of the force
- creating energy
- removing friction
Answer and explanation
changing the size or direction of the force
The work is at best the same; the machine trades force against distance.
Problem 4
- move it a shorter distance
- move it a longer distance
- reduce its weight
- remove gravity
Answer and explanation
move it a longer distance
A smaller force applied over a longer distance does the same work.
Problem 5
Answer and explanation
4
120/30 = 4, so the lever multiplies the force about fourfold.
Problem 6
Answer and explanation
Work is force times distance, and a machine reduces the force only by increasing the distance over which it acts, so the product stays the same at best. In practice friction means the work put in is slightly more than the useful work got out. A machine makes a task manageable, not cheaper in energy.
Response criteria
- State a scientifically accurate conclusion.
- Show the data, mechanism, or calculation that supports it.
- Include units, conditions, or limits where relevant.