Work Done on a Spring (OCR GCSE Physics A (Gateway))

Revision Note

Katie M

Written by: Katie M

Reviewed by: Caroline Carroll

Work Done on a Spring

  • When a spring is stretched or compressed by a force, work is done by the spring

  • Work done is the transfer of energy

    • The energy is transferred to its elastic potential energy store

Compressed and Stretched Spring, downloadable IGCSE & GCSE Physics revision notes

When a spring is stretched or compressed, there is work done and elastic potential energy is stored

  • Elastic potential energy is defined as:

    The energy stored in an elastic object when work is done on the object

  • Provided the spring is not inelastically deformed (i.e has not exceeded its limit of proportionality), the work done on the spring and its elastic potential energy stored are equal

Calculating the Work Done on a Spring

  • The work done, or the elastic potential energy stored, while stretching or compressing a spring can be calculated using the equation:

Ee = ½ × k × e2

  • Where:

    • Ee = elastic potential energy in joules (J)

    • k = spring constant in newtons per metre (N/m)

    • e = extension in metres (m)

Elastic Potential Energy, downloadable IGCSE & GCSE Physics revision notes

The elastic potential energy in a stretched spring depends on its spring constant and extension

  • This equation is only for springs that have not been stretched beyond their limit of proportionality

    • The term e2 means that if the extension is doubled then the work done is quadrupled

    • This is because 22 = 4

Worked Example

A mass is attached to the bottom of a hanging spring with a spring constant k and 0.2 J of work is done to stretch it by 4.5 cm. Calculate the spring constant, k for this spring.

Answer:

Step 1: List the known quantities

  • Work done/elastic potential energy, Ee=0.2J

  • Extension, e=4.5 cm

Step 2: Write down the relevant equation

straight E subscript straight e equals 1 half ke squared

Step 3: Rearrange for the spring constant, k

  • Multiply by 2 on both sides

2 straight E subscript straight e equals ke squared

  • Divide by e2 to make k the subject

fraction numerator 2 straight E subscript straight e over denominator straight e squared end fraction equals straight k

Step 4: Convert any units

  • The extension should be in metres

4.5 cm=0.045 m

Step 5: Substitute the values into the equation

straight k equals fraction numerator 2 cross times 0.2 over denominator open parentheses 0.045 close parentheses squared end fraction equals 198 space straight N divided by straight m

Examiner Tips and Tricks

Remember: when calculating the work done the extension, e, is squared (e2)!

Sometimes you may see x instead of e. These are interchangeable so be prepared for both!

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Katie M

Author: Katie M

Expertise: Physics

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

Caroline Carroll

Author: Caroline Carroll

Expertise: Physics Subject Lead

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.