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, using Newton’s third law, why forces between parts of a system cannot change its total momentum. (Guide: “Why forces inside a system cannot change its momentum”; Practice Q2)
- I can explain that momentum is conserved in every interaction, but a chosen system’s momentum is constant only when the net external force on it is zero. (Guide: “Choosing the system decides whether momentum changes”; Practice Q5)
- I can explain why external forces such as friction can be ignored for the short time of a collision, but not afterwards. (Guide: “Collisions and explosions”; Practice Q4(a))
- I can describe a whole system as one object moving with its centre-of-mass velocity, and say when that velocity stays constant. (Guide: “The centre-of-mass velocity”; Practice Q7(c))
Skills
- I can add signed momenta to find a system’s total momentum, and divide by the total mass to find v_cm. (Guide: “One system, one total momentum”; Practice Q1)
- I can draw a momentum bar chart for a collision and check that the system bars match. (Guide: Figure 1)
- I can use conservation of momentum to find an unknown velocity just after a collision or an explosion, including one that starts in motion. (Guide: Worked examples 1 and 2; Practice Q4)
- I can find the change in a system’s momentum from the external impulse, Δp_sys = F_net,ext Δt. (Guide: Worked example 3; Practice Q5)
- I can set up momentum conservation separately for x and y components in a two-dimensional collision or explosion. (Guide: Figure 2; Practice Q3)
- I can design a cart experiment to test momentum conservation and use a graph of p_after against p_before. (Practice Q6)
Reasoning
- I can choose a system so that its momentum is constant, and say where momentum goes when it is not. (Guide: Worked example 3; Practice Q5(b))
- I can derive a symbolic expression for a velocity after an explosion and use it to judge a claim. (Practice Q7)
- I can predict how a speed must change when a mass or angle changes in a two-dimensional set-up, without solving simultaneous equations. (Guide: “Reasoning without solving”)
All ticked? Move on to Topic 4.4, Elastic and Inelastic Collisions, or return to the course roadmap.