A Uniform Rod Weighs 40 N and Is 1

Multiple Choice

A uniform rod weighs 40 N and is 1.0 m long. It is hinged to a wall at the left end, and held in a horizontal position at the right end by a vertical string of negligible weight, as shown in the figure. What is the magnitude of the torque due to the string about a horizontal axis that passes through the hinge and is perpendicular to the rod? The hinge is very small with negligible friction.

A) 40 N ∙ m
B) 10 N ∙ m
C) 5.0 N ∙ m
D) 20 N ∙ m
E) 30 N ∙ m