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 describe power as the rate of energy change, and say whether a given process is a transfer into or out of my chosen system or a conversion inside it. (Guide: “Power is a rate of energy change”; Practice Q4(c))
- I can explain why only the component of a force along the velocity delivers power, and give an example of a force that delivers zero power. (Guide: Figure 1 and “The sign of power”; Practice Q1)
- I can explain why constant power does not mean constant force, and why a constant-power model fails at v = 0. (Guide: Worked example 2; Practice Q6(e))
Calculation
- I can find average power from a total energy change or total work and the time taken, with the unit W = J/s. (Guide: “Average power”)
- I can derive P = F·v from P = dW/dt and dW = F·dr, and calculate it from vector components. (Guide: “Instantaneous power”; Worked example 1; Practice Q1)
- I can find the net power on an object as dK/dt or as F_net·v, and use it to find how fast the speed is changing. (Guide: Worked example 1; Practice Q2)
- I can find work as W = ∫P dt, or as the area under a power–time graph, and check it against ΔK. (Guide: Worked example 3 and Figure 2; Practice Q5(b))
- I can find v(t) and x(t) for an object driven from rest at constant power, and the force at any speed from F = P/v. (Guide: Worked example 2; Practice Q3 and Q6)
Reasoning
- I can split an applied force’s power into rates of potential-energy and internal-energy gain for steady motion against friction. (Practice Q4)
- I can compare two situations at the same power, for example carts of different mass, and predict ratios of energy and speed. (Practice Q3)
- I can linearise speed–time data to test a constant-power claim and extract the power from a slope. (Practice Q6)
- I can work out what a power–time relationship says about the force, and explain why average force × average velocity is not the average power. (Guide: Worked example 3; Practice Q7)
All ticked? Unit 3 is complete. Move on to Topic 4.1, Linear Momentum, or return to the course roadmap.