(a) Define the term “lever arm” with respect to rotational motion. (b) A student…
PHYSICS · Subjective · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
(a) Define the term “lever arm” with respect to rotational motion.
(b) A student claims that the component of a force parallel to the position vector contributes to the turning effect about the origin. Explain with a suitable argument whether the claim is correct.
(c) When a force F acts at a point whose position vector with respect to an origin is r, the magnitude of the turning moment about the origin is often written in the form τ=Frsinθ. Give a clear physical interpretation of the angle θ that appears in this expression and justify why sinθ (and not cosθ) occurs in the formula.
(d) State how the sign (positive or negative) of the scalar torque is decided in planar motion and illustrate your answer with one example for each sign.