Question

Figure shows four situations in which a force acts on a box while the box slides rightward a distance d across a frictionless floor. The magnitude of the forces are identical with their orientations as shown. Identify under which condition the work done on the box during the displacement will be negative.

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

In Option(d), $\theta =0^{\circ },\cos \theta =1$ (maximum value). So, work done is maximum.
In Option(c), $\theta <{90}^{\circ },\cos \theta$ is positive. Therefore, $W$ is positive.
In Option(b), $\theta ={90}^{\circ },\cos \theta$ is zero. $W$ is $zero$.
In Option(a), $\theta$ is obtuse, $\cos \theta$ is negative. $\therefore W$ is negative.