Refer to the exercise of Problem P4.21.

(a) Measure the angle of force A directly from the diagram and use it to find the magnitude of the force at hinge B.

(b) A design condition is that the force at B should be less than 5 kN. What is the maximum force that a machinist can apply to the handle before that condition is reached?

P4.21

Channel-lock pliers hold a round metal bar as a machinist grips the handles with P = 50 N (Figure P4.21). Using the free body diagram shown for the combined lower jaw and upper handle, calculate the force A that is being applied to the bar.

Figure P4.21

130 mm 20 mm C B D B, A Bx