Hooke's law and force-extension graphsEdexcel A-Level Physics: Flashcards
What these 12 flashcards ask
- State Hooke's law.
- What is stiffness (spring constant) and its unit?
- What does the gradient of a force–extension graph give?
- What is the limit of proportionality?
- What is the elastic limit?
- What is elastic deformation?
- What is plastic deformation?
- What is the yield point?
- What does the unloading graph look like after plastic deformation?
- A spring has k = 200 N m⁻¹. What force gives an extension of 5.0 cm?
- Does F = kx apply in compression?
- Why must extension be converted to metres?
Exam questions on Hooke's law and force-extension graphs
- A helical spring obeys Hooke's law. A tensile force of 4.0 N extends it by 25 mm.The spring is instead compressed by 15 mm. Calculate the force needed, assuming Hooke's law is obeyed in compression.2 marks
- A metal wire is loaded in steps and the extension is measured. The graph of force against extension is a straight line through the origin up to a force of 12 N, where the extension is 1.5 mm. Beyond 12 N the line curves so that its gradient decreases. When the wire is unloaded from a force of 12 N it returns to its original length. When it is unloaded from a force of 14 N it is found to be 0.30 mm longer than at the start.Explain what the 0.30 mm permanent extension shows about the wire.2 marks
- A car suspension spring has a stiffness of 4.5 × 10⁴ N m⁻¹. When the car is parked, the spring supports one quarter of the car's mass of 1200 kg. The spring obeys Hooke's law up to a compression of 0.18 m. Take g = 9.81 N kg⁻¹.Calculate the compression of the spring when the car is parked.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).