GCSE Combined Science (AQA)

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Calculating Extension

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Forces Forces and elasticity

Calculating Extension

6:25 Deformations and Springs
Spec 4.5.3
Previous Elastic & Inelastic Deformations Next Force-Extension Graphs
  • The force needed to extend a spring equals the product of the spring constant and the extension of the spring.
  • Deformations like extensions occur when multiple forces act on an object.
  • To stretch a spring, forces must pull from either end.
  • The equation for force is F = K * E, where F is the force, K is the spring constant, and E is the extension.
  • The two forces applied during extension usually have the same magnitude.
  • The spring constant (K) measures how stiff the spring is.
  • Extension (E) is the difference between the spring's length before and after applying forces.
  • Common mistake: E is not the length of the extended spring, but the difference in length.
  • Forces are measured in Newtons, extension in meters, and spring constant in Newtons per meter.
  • The equation holds if the force is below the spring's limit of proportionality.
  • Example: A 15 Newton weight extends a spring by 25 cm; convert to meters for calculations.
  • Rearrange the equation to find the spring constant: K = F / E.
  • Example calculation: Spring constant = 15 Newtons / 0.25 meters = 60 Newtons per meter.
  • Spring constant is a property of the spring and remains constant for different weights/extensions.
  • The same equation applies to compressions, using compression instead of extension.
  • For compressions, the equation is F = K * compression, with similar units and conditions.
  • The equation for both extensions and compressions holds if the force is below the spring's limit of proportionality.

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