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 the contact force from a surface into a normal component and a friction component, and say which way each points. (Guide: “What a surface does to an object”)
- I can decide whether friction is kinetic or static by asking whether the two surfaces slide relative to each other. (Guide: table; Practice Q2)
- I can find the direction of kinetic friction on each of two sliding surfaces, including the third-law partner. (Guide: “Kinetic friction”; Practice Q2)
- I can explain why contact area does not appear in the friction equations, and that μ depends on the materials. (Guide: “Why contact area does not matter”)
- I can explain why μ_s is usually larger than μ_k and what that means for starting and keeping an object moving. (Guide: Worked example 1)
Calculation
- I can find the normal force from the perpendicular forces, including an angled pull or push and a slope. (Guide: Worked examples 2 and 3; Practice Q3)
- I can calculate kinetic friction with F_f,k = μ_k F_n and use it in Newton’s second law. (Guide: Worked example 1; Practice Q4, Q5)
- I can find static friction from a force balance, and check it against the maximum μ_s F_n. (Guide: Worked examples 1 and 3; Practice Q1, Q3)
- I can find μ_s from the angle at which an object just slips, μ_s = tan θ. (Guide: Worked example 3; Practice Q6)
Reasoning
- I can sketch how friction changes as an applied force grows from zero until the object slides, with the drop from static to kinetic. (Guide: Figure 1; Practice Q5)
- I can explain why static friction can point in the direction of motion, using walking or an accelerating vehicle. (Guide: “Friction can point the way you move”; Practice Q7)
- I can compare two situations, such as pulling up or pushing down at an angle, and explain the difference through the normal force. (Guide: Worked example 2)
- I can design a procedure to measure μ_s and say how to reduce uncertainty. (Practice Q6)
All ticked? Move on to Topic 2.8, Spring Forces, or return to the course roadmap.