work done by friction

Question

A 2 kg block slides 3 m on rough horizontal surface (μ_k = 0.4, g = 10). Work done by friction?

RankGuru · Accepted Answer

1. **Friction Force**: $f_k = \mu_k N$. For a horizontal surface $N = mg$.
2. **Calculation of Force**:
   - $f_k = 0.4 	imes (2 	imes 10) = 8$ N.
3. **Directionality**: Friction always acts opposite to the direction of motion, so the angle $	heta = 180^\circ$ (or $\cos 	heta = -1$).
4. **Work Calculation**:
   - $W = f_k 	imes d 	imes \cos(180^\circ)$
   - $W = 8 	imes 3 	imes (-1) = -24$ J.
5. **Outcome**: Kinetic friction does **$-24$ J** of work (energy is removed from the system).

Rank Guru

work done by friction

Select the correct option: