EasyPhysicsHigh School (11–12)Heat & Thermodynamics › Temperature and Thermal ExpansionConceptualBoard Exam

Answer, and give a reason. A metal lid on a glass jar is stuck…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

Answer, and give a reason.

A metal lid on a glass jar is stuck. Why does running hot water over the lid help?
Why are power lines hung with some sag in summer?
A steel ring is a little too small to slip over a steel rod. Should you heat the ring or the rod?

Need a reminder? The key ideaShow

Thermal expansion: $\Delta L = \alpha L\,\Delta T$ , $\Delta A = 2\alpha A\,\Delta T$ , $\Delta V = \gamma V\,\Delta T$ with $\gamma = 3\alpha$ for solids. Steel $\alpha = 1.2 \times 10^{-5}\ \text{K}^{-1}$ ; mercury $\gamma = 1.8 \times 10^{-4}\ \text{K}^{-1}$ .

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.

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