Torque and Rotational Dynamics practice quiz

Key ideaω = dθ/dt and α = dω/dt. The constant-α equations mirror the linear ones.

Common mistakeUsing degrees or revolutions where the equations need radians.

Key ideaτ = r × F, with magnitude rF sin θ (force times lever arm). The direction comes from the right-hand rule.

Common mistakeUsing the distance to the force’s point of application instead of the perpendicular lever arm.

Key ideaI = Σmr² or ∫r² dm. Parallel-axis theorem: I = I_cm + Md².

Common mistakeApplying the parallel-axis theorem from an axis that isn’t through the center of mass.

Key ideaFor static equilibrium, ΣF = 0 and Στ = 0 about any point. Choosing the pivot at an unknown force removes it from the torque equation.

Common mistakeForgetting the object’s own weight acting at its center of mass, or choosing a pivot that leaves two unknowns.

Key ideaΣτ = Iα about a fixed axis or the center of mass. Link it to the linear motion with a = rα.

Common mistakeAssuming the tension in a string over a massive pulley is the same on both sides.