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 state the condition for rotational equilibrium, Στ = 0, and explain that it means constant angular velocity, not necessarily rest. (Guide: “Newton’s first law in rotational form”)
- I can explain why a steadily spinning fan has zero net torque on it. (Guide: Figure 2)
- I can state that unbalanced torques always mean the angular velocity is changing, even at an instant when ω = 0. (Guide: “Unbalanced torques”; Practice Q3)
- I can give one example of translational equilibrium without rotational equilibrium, and one of the reverse. (Guide: “The two kinds of equilibrium are independent”; Practice Q2, Q7)
Skills
- I can draw a force diagram that puts each force at the point where it acts, with the weight of a uniform object at its centre. (Guide: Figure 1)
- I can choose a pivot that removes an unknown force and write Στ = 0 with a stated sign convention. (Guide: Worked example 1; Practice Q1, Q4)
- I can use only the perpendicular part of an angled force when finding its torque. (Guide: Worked example 2)
- I can combine Στ = 0 with ΣF = 0 to find every unknown force on a beam or rod. (Guide: Worked examples 1 and 2; Practice Q4)
- I can find the condition for an object to start tipping by setting the force at one support to zero. (Practice Q4)
- I can derive a symbolic expression for a force in equilibrium and predict how it changes when a distance changes. (Guide: Worked example 2; Practice Q5)
Reasoning
- I can sketch an angular velocity–time graph and mark where the net torque is zero and where it is not. (Guide: Figure 2; Practice Q3)
- I can linearise balance data and use the slope to support or refute a torque model. (Practice Q6)
- I can show that a couple gives the same torque about any point. (Practice Q7)
All ticked? Move on to Topic 5.6, Newton’s Second Law in Rotational Form, or return to the course roadmap.