EasyPhysicsHigh School (11–12)Mechanics › Elasticity and Mechanical Properties of SolidsNumericalBoard ExamA-Level
A wire stretches by 1.5 mm under a load…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A wire stretches by under a load. What is the stretch if
- the wire is twice as long;
- its radius is doubled;
- the load is tripled;
- it is made of a material with twice its Young's modulus?
Each change is made on its own.
Need a reminder? The key ideaShow
Young's modulus: . A wire stretches and acts as a spring with . A wire breaks when its stress reaches the breaking stress, whatever its length.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) : .
Step 2. (b) : .
Step 3. (c) : .
Step 4. (d) : .
Answer: (a) . (b) . (c) . (d) .
Watch out. Doubling the radius quarters the stretch; it does not halve it.
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