^Sign of work

^Sign of work

1. Sign of work depends on sign of cosθ. As cosθ can be 0, +ve or – ve (recall –1 ≤ cosθ ≤ +1), hence the work done by a force also can be 0, + ve or – ve depending upon the angle between the force and the displacement.
2. Work done by a force acting at acute angles to displacement of a system is +ve.
3. Work done by a force acting at obtuse angles to displacement of a system is – ve.
4. +ve work increase the KE of the system.
5. – ve work decrease the KE of the system.