Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can split a contact force into a normal part and a friction part, and say which way the normal force points. (Guide: “Two parts of one contact force”)
- I can state when kinetic friction acts and give its direction on each surface from their relative motion. (Guide: Worked example 2; Practice Q2)
- I can explain why static friction takes whatever value prevents slipping, and why μ_s F_N is only its maximum. (Guide: “Static friction: no sliding”)
- I can explain that μ depends on the materials, that μ_s is usually larger than μ_k, and that contact area does not affect friction. (Practice Q3, Q6(e))
Calculation
- I can find the normal force from Newton’s second law perpendicular to the surface, including with extra pushes or an accelerating floor. (Practice Q1, Q7)
- I can find when an object starts to slip under a force that grows with time, and integrate its motion afterwards. (Guide: Worked example 1)
- I can derive F_N = mg cos θ, the no-slip condition tan θ ≤ μ_s and a_x = g(sin θ − μ_k cos θ) for a slope. (Guide: “Friction on a slope, symbolically”; Practice Q4)
- I can use a_x = v_x dv_x/dx when friction varies with position. (Practice Q5)
Reasoning
- I can test for slipping by assuming no slip, finding the friction needed and comparing it with μ_s F_N. (Guide: Worked example 2; Practice Q4(c))
- I can plot friction against normal force from data, find μ_k from the slope, and describe how to measure μ_s. (Practice Q6)
- I can correct the claims “friction always opposes motion” and “friction depends only on mass”. (Guide: “Common misconceptions”; Practice Q7)
All ticked? Move on to Topic 2.8, Spring Forces, or return to the course roadmap.