A 20-kg box is pushed across a horizontal floor with a horizontal force of 100 N. The coefficient of kinetic friction between the box and the floor is 0.30. What is the box's acceleration? Use g = 9.8 m/s².
A2.06 m/s²
B5.0 m/s²
C2.94 m/s²
D0.30 m/s²
Explanation
📌 Normal force N = mg = 20 × 9.8 = 196 N. Friction f = μN = 0.30 × 196 = 58.8 N. Net force = 100 − 58.8 = 41.2 N. Acceleration = 41.2/20 = 2.06 m/s². Distractor B ignored friction entirely (100/20 = 5); C used friction alone (58.8/20 = 2.94); D just reported the coefficient μ.