A 4.0 kg box of fruit slides 8.0 m down a ramp, inclined at 30.° from the horizontal. If the box slides at a constant velocity of 5.0 m/s, the work done by gravity is
A) +78. J.
B) 0.16 kJ.
C) -78. J.
D) zero.
E) -0.16 kJ.
B
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