EasyPhysicsHigh School (11–12)Mechanics › Elasticity and Mechanical Properties of SolidsMechanics › Work, Energy and PowerConceptualBoard Exam
Answer, and give a reason. A stretched wire snaps…
Contributed by StemPy LabTry 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 stretched wire snaps. Where does its elastic energy go?
- A bow is drawn back twice as far. How much more energy can it give the arrow?
- Why do long-distance runners prefer shoes with springy soles?
Need a reminder? The key ideaShow
Elastic energy: . Per unit volume, .
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) Into the motion of the two loose ends (they whip back), and then into sound and heat.
Step 2. (b) Four times as much, since , if the bow still obeys Hooke's law.
Step 3. (c) A springy sole stores energy as the foot lands and returns most of it as the foot pushes off, so less is wasted as heat.
Answer: (a) Motion, sound and heat. (b) Four times. (c) The sole gives energy back.
Watch out. A sole that is soft but not springy (with a big loop) turns the energy into heat instead.
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