Equilibrium: A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle ? below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to
A. W.
B. W + P.
C. W + P cos ?.
D. W + P sin ?.
E. W - P sin ?.
Answer: D
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