โš›๏ธ Physics Quiz 4: Friction, Springs, and Applied Forces

โš›๏ธ Physics ยท Quiz 004

Apply force models to static and kinetic friction, Hooke's law, springs, and combined applied forces.

Learning goalApply Newtonian dynamics to contact forces and elastic restoring forces, including threshold and multi-force situations.

  • 5 questions
  • Foundation
  • Explanations after finishing
Answered 0/5
FoundationFor an ideal spring operating in its linear elastic range, which expression gives the restoring force along the spring axis?
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A restoring force points back toward equilibrium and is proportional to displacement in the linear range.

UnderstandingA 5 N horizontal push is applied to a crate, but the crate remains at rest. No other horizontal force acts except static friction. What is the static-friction force?
Need a small nudge?

Static friction adjusts to whatever value is needed to prevent motion, up to its maximum.

ApplicationA spring with force constant k = 200 N/m is stretched 0.030 m from equilibrium. What is the magnitude of the restoring force?
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Use the magnitude form of Hooke's law with the spring constant and displacement.

InterpretationA 5.0 kg crate slides on a horizontal floor with coefficient of kinetic friction 0.20. A 30 N horizontal force pulls it forward. Use g = 10 m/s^2. What is its acceleration?
Need a small nudge?

Find the normal force, then kinetic friction, then the horizontal net force.

ConnectionA 10 kg crate rests on a horizontal surface with coefficient of static friction 0.40. It is attached to a horizontal spring with k = 100 N/m that is stretched slowly. Use g = 10 m/s^2. What is the largest spring extension for which the crate can still remain at rest?
Need a small nudge?

At the threshold of slipping, the spring force equals the maximum static-friction force.

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