Physics 111 HW 19
assigned 13 April 2012
T00A. Explain why torque is important when describing the performance of an automobile.
T00B. Weakman isn’t very strong. He can only apply a maximum force of 100 N to anything. He-man is strong, and can apply a maximum force of 10000 N to anything. Is it possible for Weakman to exert a greater torque on an object than He-man? Explain.
T00C. Calculate the torque (magnitude and direction) about point O due to the force F in each of the situations sketched in the figure at right. In each case, the force F and the rod both lie in the plane of the page, the rod has a length 4.00 m, and the force has magnitude F = 10.0 N.
T00D. A square metal plate 0.180 m on each side is pivoted about an axis through point O at its center and perpendicular to the plate (see figure at right). Calculate the net torque about this axis due to the three forces shown in the figure if the magnitudes of the forces are F1 = 18.0 N, F2 = 26.0 N, and F3 = 14.0 N. The plate and all forces are in the plane of the page.
T00E. A weekend plumber, unable to loosen a pipe fitting, slips a piece of scrap pipe (a “cheater”) over his wrench handle. He then applies his full weight of 900 N to the end of the cheater by standing on it. The distance from the center of the fitting to the point where the weight acts is 0.80 m, and the wrench handle and cheater make an angle of 19o with the horizontal (see figure). The pipe has a diameter of 6 cm.
a) Find the magnitude and direction (not just CW or CCW, but the actual direction) of the torque he applies about the center of the pipe fitting.
b) If the fitting doesn’t budge, what is the frictional torque?
c) If the µs between the fitting and the pipe is 0.5, determine the normal force between the fitting and the pipe.
T01. Calculate the net torque about point O for the two forces applied as in the figure. The rod and both forces are in the plane of the page, and assume the rod has negligible weight.