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 explain why angular momentum only has a meaning once an axis or reference point is chosen, and show that the same object has different L about different points. (Guide: Worked example 2(d); Practice Q7(d))
- I can explain why an object moving in a straight line at constant velocity has a constant, nonzero angular momentum about a point off its path. (Guide: Figure 1; Practice Q7)
- I can state that angular impulse points the same way as the torque, and tell apart the areas under τ–t and τ–θ graphs. (Guide: “Angular impulse”)
Calculation
- I can calculate L = Iω for a rigid body on a fixed axis, with a sign. (Guide: “Angular momentum of a rigid body”; Practice Q2)
- I can calculate L for a point object from rmv sin φ, from mvd, or from L_z = x p_y − y p_x. (Guide: “Angular momentum of a point object”; Practice Q1)
- I can find the angular impulse of a time-dependent torque by integration, and use it with L₀ to find a later ω. (Guide: Worked example 1; Practice Q4)
- I can estimate an angular impulse from torque–time data and use it to judge friction. (Practice Q6)
Reasoning
- I can derive τ_net = dL/dt from τ_net = Iα and state the constant-I condition, and derive d(r × p)/dt = r × F_net for a point object. (Guide: “The rotational impulse–momentum theorem”; Practice Q5)
- I can read net torque from the slope of an L–t graph and sketch an L–t graph from a τ–t graph. (Guide: Figure 2; Practice Q3, Q4(c), Q6(e))
- I can compare the change in angular momentum and the change in ω for bodies given the same angular impulse, including when a body reverses direction. (Guide: “Comparing initial and final values”; Practice Q2)
- I can show that the torque of gravity about a chosen point changes a falling object’s angular momentum. (Guide: Worked example 2)
All ticked? Move on to Topic 6.4, Conservation of Angular Momentum, or return to the course roadmap.