Question

A body moves a distance of $10\text{m}$ along a straight line under the action of a force $5\text{N}$. If the work done is $25\text{joule}$, the angle which the force makes with the direction of motion of body is:

• A. $0^{\circ }$
• B. ${30}^{\circ }$
• C. ${60}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is C ${60}^{\circ }$

Work done in case of constant force$=\overrightarrow{F}.\overrightarrow{S}$
It is given that work done is $25\text{J}$
$\overrightarrow{F}.\overrightarrow{S}=25$
$FS\cos \theta =25$
$\left(5\right)\left(10\right)\cos \theta =25$
$\cos \theta =\frac{1}{2}$
$\theta ={60}^{\circ }$

Why this question? "Work done by a constant force is given by $|\overrightarrow{F}||\overrightarrow{S}|\cos \theta$" "Positive work done indicates that angle between $\overrightarrow{F}\&\overrightarrow{S}$ is acute"