In each of the following cases,a force,$F$ is acting on an object of mass,$m$. The direction of displacement is from west to east,shown by the longer arrow. Observe the diagrams carefully and state whether the work done by the force is negative,positive,or zero.

(N/A) The work done by a force is given by the formula $W = F \cdot s \cdot \cos(\theta)$,where $\theta$ is the angle between the force and the displacement.
$1$. In the first case,the force $F$ is acting vertically upwards while the displacement is horizontal (west to east). The angle between them is $90^{\circ}$. Since $\cos(90^{\circ}) = 0$,the work done is zero.
$2$. In the second case,the force $F$ is acting in the same direction as the displacement (west to east). The angle between them is $0^{\circ}$. Since $\cos(0^{\circ}) = 1$,the work done is positive.
$3$. In the third case,the force $F$ is acting in the opposite direction to the displacement (east to west). The angle between them is $180^{\circ}$. Since $\cos(180^{\circ}) = -1$,the work done is negative.