Question

A bomb of mass 30kg at rest explodes into two pieces of masses 18kg and 12kg the velocity of 18kg mass is 6ms-1 the kinetic energy of other mass is

Answer 1

Answer:

Kinetic energy of the other mass is 486J

Explanation:

According to the conservation of momentum,

m1u1 + m2u2 = m1v1 + m2v2

Since it is at rest,

(m1 + m2)u = m1v1 + m2v2

30(0) = 18(6) + 12(x) [ Where x is velocity of other mass]

0 = 108 + 12(x)

x = -108/12

x = -9m/s

Kinetic energy = (1/2)(m)(v^2)

=> (6)(-9)^2

=>486J

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Answer 2

Answer:

486 Joule

Explanation:

Since, momentum in an isolated system remains conserved , therefore the 12 kg mass will move in the opposite direction with the same vè as the 18kg mass , in order to make the net momentum of the system 0

we may proceed ,

m1v1 = -m2v2

=>V2 = -m1v1/m2 = - 18 × 6/12 = -9 m/s

Therefore K.E of 12 kg piece,

½mv²= ½ × 12 × 81 = 486 Joule