Center Of Mass Momentum And Collision Question 1

Question 1 - 25 January - Shift 2

A body of mass $1 kg$ collides head on elastically with a stationary body of mass $3 kg$. After collision, the smaller body reverses its direction of motion and moves with a speed of $2 m / s$. The initial speed of the smaller body before collision is $ms^{-1}$.

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Answer: (4)

Solution:

Formula: Conservation of Momentum

$1 \times u_1=-2+3 v \Rightarrow u_1=-2+3 v$

$1=\frac{v+2}{u_1} \quad \Rightarrow v+2=u_1$

Solving (1) and (2)

$u_1=4 m / s$