Long answer·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 light platform is suspended by four identical steel wires. Each wire has length , area , and Young's modulus . A load of is placed symmetrically on the platform.
Total: 4 marks
(a) Find the force carried by each wire. (1 mark)
(b) Find the extension of each wire. (2 marks)
(c) State why the symmetry condition matters. (1 mark)
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