Work Energy and Power - Result Question 65

68. A body of mass $m$ moving with velocity $3 km /$ $h$ collides with a body of mass $2 m$ at rest. Now the coalesced mass starts to move with a velocity

[1996]

(a) $1 km / h$

(b) $2 km / h$

(c) $3 km / h$

(d) $4 km / h$

Show Answer

Answer:

Correct Answer: 68. (a)

Solution:

  1. (a) Applying law of conservation of momentum,

$m_1 u_1+m_2 u_2=(m_1+m_2) v$

or, $m_1 u_1=(m_1+m_2) v \quad(\because u_2=0)$

$\Rightarrow m \frac{(3 \times 1000)}{3600}=3 m(v)$

$\Rightarrow v=\frac{1000}{3600} m / s=1 km / hr$