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) $4 km / h$
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Answer:
Correct Answer: 68. (a)
Solution:
- (a) Applying law of conservation of momentum,
$m_1 u_1+m_2 u_2=(m_1+m_2) v$
or, $m_1 u_1=(m_1+m_2) v \quad(\because u_2=0)$
$\Rightarrow m \frac{(3 \times 1000)}{3600}=3 m(v)$
$\Rightarrow v=\frac{1000}{3600} m / s=1 km / hr$
