Friction: A 150-N box is being pulled horizontally in a wagon accelerating uniformly at 3.00 m/s². The box does not move relative to the wagon, the coefficient of static friction between the box and the wagon's surface is 0.600, and the coefficient of kinetic friction is 0.400. The friction force on this box is closest to A) 450 N. B) 90.0 N. C) 60.0 N. D) 45.9 N.

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Quizplus · Accepted Answer

The friction force is kinetic friction, which is given by:$$f_k=\mu_k n$$where:$$f_k$$ is the kinetic friction force$$\mu_k$$ is the coefficient of kinetic friction$$n$$ is the normal forceThe normal force is equal to the weight of the box:$$n=mg$$where:$$m$$ is the mass of the box$$g$$ is the acceleration due to gravitySubstituting these values into the equation for kinetic friction, we get:$$f_k=\mu_k mg$$$$f_k=0.400(150 	ext{ N})(9.81 	ext{ m/s}^2)$$$$f_k=58.86 	ext{ N}$$The friction force is closest to 45.9 N, which is choice D.

Friction: a 150-N Box Is Being Pulled Horizontally in a Wagon