MCQ
A body of mass $10\,kg$ moving with speed of $3 \,ms ^{-1}$ collides with another stationary body of mass $5 \,kg$. As a result, the two bodies stick together. The $KE$ of composite mass will be .......... $J$
  • A
    $60$
  •  $30$
  • C
    $90$
  • D
    $120$

Answer

Correct option: B.
 $30$
b
(b)

Using momentum conservation

$10(3)=15 \,V$

$V=2 \,m / s$

$K . E .=\frac{1}{2} m v^2=\frac{1}{2}(15)(2)^2$

$=30 \,J$

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