Question

A body of mass m moving with velocity ui, collides elastically with a stationary body of mass 3m as shown . If velocity of m after collision is vj as shown
The value of v is

u/√2
u/√3
u/2
u/3

Answer 1

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Answer 2

A body of mass m moving with velocity u i, collides elastically with a stationary body of mass 3m as shown in figure.

To find : if the velocity of m after collision is v j , then the value of v is ....

solution : from conservation of linear momentum,

initial momentum = final momentum

⇒mu i + 0 = m vj + 3m v'

⇒v' = u/3 i - v/3 j

from conservation of energy,

initial kinetic energy = final kinetic energy

⇒1/2 mu² + 0 = 1/2 m v² + 1/2 3m(u²/9 + v²/9)

⇒u² = v² + u²/3 + v²/3

⇒u² - 2u²/3 = v²

⇒v = u/√3

Therefore the value of v = u/√3