A body moves 20 cm when 90 N of force is applied to it. If the work done in this process is 18 J, what angle should there be between the force and the displacement?

We know that work is the dot product of Force and Displacement.

$\mathrm{W}=\mathrm{F}·\mathrm{d}=\mathrm{Fdcos}\theta$

Here W is the work done, F is the force, d is the displacement and $\theta$ is the angle between F and d.

Given:
 W= 18 J
F = 90 N
d = 20 cm = 0.2 m

Work done is given by:
$\mathrm{W}=\mathrm{F} \mathrm{D} \mathrm{cos\theta }$
$18=90\times 0.2\times \cos \theta$
$1 = \cos \theta$
$\cos 0° = \cos \theta$
$\therefore$$\theta =0°$

Therefore, the angle between the force and displacement must be $0°$