A stone of mass 0.4 kg is projected horizontally at a speed of 6.0 m s−1 from the top of a wall, 5.0 m above the surrounding ground. When it arrives at the ground its speed is 10 m s−1. How much energy is lost by the stone in falling through the air?
A 2.4 J
B 6.8 J
C 12.8 J
D 14.4 J
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