In the formula “Work = Fs cos θ”, if the angle θ between force and displacement is more than 90°, the net work done will be:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Negative
In \(W=Fs\cos\theta\), the force \(F\) and the displacement \(s\) are magnitudes and are always positive, so the sign of the work is the sign of \(\cos\theta\).
For \(0^\circ\le\theta\lt90^\circ\), \(\cos\theta\) is positive, so the work is positive
At \(\theta=90^\circ\), \(\cos\theta=0\), so no work is done
For \(90^\circ\lt\theta\le180^\circ\), \(\cos\theta\) is negative, so the work done is negative
Negative work means the force opposes the motion and takes energy away from the body, as friction does on a sliding block.