A 2 kg block on a horizontal surface has kinetic friction with μk = 0.3. What is the magnitude of the kinetic friction force?

A 2 kg block on a horizontal surface has kinetic friction with μk = 0.3. What is the magnitude of the kinetic friction force?

• A. 11.76 N
• B. 5.88 N
• C. 2.94 N
• D. 7.50 N

Answer: (B)

Frictional force exercising kinetic friction follows F_k = μk N. On a horizontal surface, the normal force equals the weight, so N = mg. With m = 2 kg and g ≈ 9.8 m/s^2, N = 2 × 9.8 = 19.6 N. Then F_k = μk N = 0.3 × 19.6 = 5.88 N. So the magnitude is 5.88 newtons, directed opposite the motion. The other numbers would require a different μk or a different normal force, but with the given data this is the correct result.

Frictional force exercising kinetic friction follows F_k = μk N. On a horizontal surface, the normal force equals the weight, so N = mg. With m = 2 kg and g ≈ 9.8 m/s^2, N = 2 × 9.8 = 19.6 N. Then F_k = μk N = 0.3 × 19.6 = 5.88 N. So the magnitude is 5.88 newtons, directed opposite the motion. The other numbers would require a different μk or a different normal force, but with the given data this is the correct result.