Question

A MACHINE ,RATED 150 W, CHANGES ITS VELOCITY OF A 10KG MASS FROM 4 TO 10 M/S IN 4S.THE EFFICIENCY OF MACHINE IS NEARLY

Answer 1

Answer:

70%

Explanation:

efficiency (e) = Power delivered / Power rating

Power delivered (P) = Work (W) / time (t)

W = Change in Kinetic Energy

KE = (1/2)m(v^2)

Final KE = (1/2)*10*(10*10) = 500 J

Initial KE = (1/2)*10*(4*4) = 80 J

W = 500 - 80 = 420 J

Power delivered = Work / time = 420/4 = 105 W

Power rating = 150 W (Given)

efficiency = 105/150 = 0.7 = 70%