A mechanic uses a wrench of fixed length to loosen a bolt
PHYSICS · Multi-part · CBSE · Physics · System of Particles and Rotational Motion · System of Particles and Rotational Motion
Problem
A mechanic uses a wrench of fixed length to loosen a bolt. She varies only the direction in which she pulls, keeping the magnitude of the applied force constant. Consider the graph of torque magnitude τ on the vertical axis versus the angle θ between the wrench handle and the applied force on the horizontal axis for 0∘≤θ≤180∘. The graph is a smooth, symmetric curve that is zero at θ=0∘ and θ=180∘ and has a single maximum at θ=90∘.
(a) Explain why the torque is zero when θ=0∘ even though a non-zero force is applied.
(b) Describe, without calculation, why the torque reaches its maximum at θ=90∘.
(c) The graph is symmetric about θ=90∘. Explain the physical reason for this symmetry.
(d) If the mechanic were to reverse the direction of the force (push instead of pull) while keeping its line of action unchanged, describe qualitatively how the τ–θ graph would change, if at all.