A mechanic must apply a torque to loosen a bolt using a wrench
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A mechanic must apply a 50N⋅m torque to loosen a bolt using a wrench. The wrench handle is 0.25m long, measured from the center of the bolt to the point where the mechanic grips the handle.
(a) The mechanic pulls in a direction perpendicular to the handle. Calculate the minimum force required to loosen the bolt.
(b) In a cramped space the mechanic can apply a maximum force of only 120N and can pull at most 30∘ away from perpendicular to the handle. Determine how far from the bolt’s center along the handle the mechanic must grip so that the bolt can still be loosened.
(c) Explain why pulling at an angle away from perpendicular requires either a larger force or a larger distance from the bolt to achieve the same torque.
(d) Suppose an extension bar is slipped over the wrench handle, effectively increasing its length by 0.15m. Describe quantitatively how this changes the minimum perpendicular force needed to achieve the required torque in part (a).