Elastic Strain Energy and Force-Extension Graphs · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Banking energy in a stretch

Science · Matter & Materials · ages 17-18
Name ______________________   Date ____________

  1. Loading and unloading curves enclose a loop. What does the loop area tell you?

    • A drawing error to ignore
    • Energy lost as heat each cycle
    • Extra energy created by rubber

  2. A spring is pulled with 10 N to 0.2 m along a straight graph from the origin. How much energy in joules is stored?

    Answer: ______________

  3. The area under a force against extension graph equals the work done stretching the sample.

    Circle one:   True   False

  4. A stretched spring fires a mass with no other losses. Which equation gives the launch speed?

    • Half F x equals half m v squared
    • F times x equals m times v
    • Energy equals force plus speed

  5. Loading stores 6 J and unloading returns 4 J. How many joules never came back?

    Answer: ______________

  6. A metal wire is stretched gently, well within its elastic range. What happens on unloading?

    • It stays permanently longer
    • It snaps at once
    • It springs back with almost no loop

  7. Lee prices a straight-from-origin spring graph at F times x. What is his error?

    • He should square the force
    • He should use a ruler
    • He forgot the half, the area is a triangle

  8. A spring stores 1 J and fires a 0.5 kg ball with no other losses. What launch speed in metres per second results?

    Answer: ______________

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Answer key

For grown-ups. Fold this page away before handing over the rest.

Banking energy in a stretch W1-mt_4WnFUmR13O-s1

  1. Energy lost as heat each cycle · Unloading returns less than loading gave, and the loop area is that lost heat.
  2. 1 · The triangle area is half times 10 times 0.2, which is 1 joule.
  3. True · That area is exactly the banked work, held as strain energy while elastic.
  4. Half F x equals half m v squared · Banked strain energy converts into kinetic energy, so the two halves match.
  5. 2 · Subtract the return from the outlay: 6 minus 4 is 2 joules lost as heat.
  6. It springs back with almost no loop · Gentle pulls stay elastic, so unloading retraces loading and returns the energy.
  7. He forgot the half, the area is a triangle · A straight line from the origin bounds a triangle, so the area needs the half.
  8. 2 · Set 1 equal to half times 0.5 times v squared: v squared is 4, so v is 2.
Worksheet · LightMySky