A Uniform Rod Weighs 40 N and Is $5.0 \mathrm {~N} \cdot \mathrm { m }$

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) $5.0 \mathrm {~N} \cdot \mathrm { m }$
B) $20 \mathrm {~N} \cdot \mathrm { m }$
C) $40 \mathrm {~N} \cdot \mathrm { m }$
D) $30 \mathrm {~N} \cdot \mathrm { m }$
E) $10 \mathrm {~N} \cdot \mathrm { m }$