Friction — Work DoneMediumQuestion 30254
Question
A block slides 5 m on a rough surface (μₖ = 0.2, mass = 4 kg, g = 10 m/s²). Work done by friction is:
- A−4 J
- B−40 JCorrect
- C40 J
- D−8 J
Correct answer
−40 J
Explanation
Friction force = μₖmg = 0.2×4×10 = 8 N. Work = −Fd = −8×5 = −40 J (negative because friction opposes motion).