It takes 40 J of energy to push a large box 4m across a floor. Assuming the push is the same direction as the movement, what is the magnitude of the force of the box?

10 N

Explanation:

Work done is the dot product of the force magnitude with distance and cosine of the angle betweenthem.

Equation to use: W=|F|*|d|*cosθ

Your unknown is the force F; You have one equation, oneunknown.

40j=(F)*(4m)*cos(0)

F=40j/4m

F=10N

t = 1/400 h   ⇔ 0.0025 h ⇔ 9s ⇔ 0.15 m

any of the answers are correct.