Question

A force F acts on an object undergoing a displacement s, the force being oriented at an angle θ with respect to the displacement. Which one of the following correctly describes ALL of the circumstances under which the work done by the force is zero? Entry field with incorrect answer a) The displacement is zero, or the angle is 90°. b) The force is zero, or the displacement is zero, or the angle is 90°. c) The force is zero, or the angle is 90°. d) The force is zero, or the displacement is zero, or the angle is 180°. e) The force is zero, or the displacement is zero.

Answer 1

Answer:

b) The force is zero, or the displacement is zero, or the angle is 90°.

Explanation:

The work done by a force F, acting on an object undergoing a displacement s, is given by:

$W=Fscos\theta$

$\theta$ is the angle between the force and the displacement. Thus, the work is zero, when the force is zero, or the displacement is zero, or the angle is 90°, since the cosine of this angle is zero.