Work done is a scalar quantity. Its SI unit is joule(J).

Other units of work done are:

1 erg = 10⁻⁷ J

1 kWh = 3.6 × 10⁶ J

When a constant force F acts on a body through a displacement d, the work done

$$W = Fd$$

W = Work done

F = Force

d = Displacement in the direction of the force

If displacement d makes an angle θ with the force F, then we have,

$$W = Fd\cos\theta$$

If the displacement is made in the opposite direction of the force, then θ = 180^∘ and hence work done

W = Fd cos θ = - Fd