Case study·Hard exam skill (4/5)·No calculator
Difficulty guide
The label describes the problem, not your ability.
1/5 - Foundational
Warm-up setup; checks one basic idea.
2/5 - Routine exam skill
Normal syllabus skill; usually one main rule or interpretation.
3/5 - Standard multi-step
Exam-style problem with multiple steps or a common trap.
4/5 - Hard exam skill
High-end exam problem; combines methods carefully.
5/5 - Challenge
Stretch problem beyond normal exam pressure.
Question
A student pushes a box with a horizontal force of . Friction from the floor is opposite to the push.
Total: 4 marks
(a) Find the net force on the box. (1 mark)
(b) Find the acceleration. (1 mark)
(c) State how the acceleration would change if the floor were rougher. (1 mark)
(d) Explain why friction is not always useless. (1 mark)
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