E(P)=m*g*h
   =42*10*1
   =420 J
E(P)=E(K)
E(K)=1/2MV^2
 420=½*42*V^2
V^2=20
V=4.47
"Velocity is essentially a vector quantity. It is the rate of change of distance. It is the rate of change of displacement. Speed of an object moving can never be negative. The velocity of a moving object can be zero. "
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