Question

a classmate is attempting to draw a free body diagram for a box being pushed across the floor at a constant speed. the image below is what they have drawn so far.which (if any) of their forces have been drawn incorrectly?a there is nothing wrong with the free body diagramb the applied force should be the same size as the friction forcec the normal force should be larger than the force of gravityd the friction force should be in the same direction as the applied force

Explanation:

Step1: Analyze the vertical forces

Since the box is on a horizontal floor and not accelerating vertically, according to Newton's first law (\(F = ma\), \(a_y=0\)), the normal force \(F_N\) and the weight \(F_w\) (force of gravity) are equal in magnitude (\(F_N = F_w\)).

Step2: Analyze the horizontal forces

The box is moving at a constant speed. Using Newton's first law (\(F = ma\), \(a_x = 0\)), the net force in the horizontal direction is zero. So the applied force \(F_a\) and the friction force \(F_f\) must be equal in magnitude (\(F_a=F_f\)) and opposite in direction.

Answer:

B. The applied force should be the same size as the friction force