Question

The velocity of a body of mass 0.8 kg is 3i + 4j m/s. So its kinetic energy is ................... .
(A) 10 J
(B) 40 J
(C) 32 J
(D) 16 J

Answer 1

v = 3i +4j

v.v = (3i +4j).(3i +4j) = 9+16 = 25

KE = (0.5)*0.8*25 = 10 J

Answer 2

Answer:A = 10J

Explanation:

V= 3i+4j

Therefore, v.v=v^2

=(3i+4j)(3i+4j)

=3ix3i=9

=4jx4j=16

V.V= 9+16=25

K.E= 0.5 X 0.8 X 25

= 10J

Hope it helps!

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