Q. An explosion blows a rock into three parts. Two parts go off at right angles to each other. These two are, $1\ kg$ first part moving with a velocity of $12\ ms^{- 1}$ and $2\ kg$ second part moving with a velocity of $8\ ms^{- 1}$. If the third part files off with a velocity of $4\ ms^{- 1}$, its mass would be
A) $5\ kg$
B) $7\ kg$
C) $17\ kg$
D) $3\ kg$
Explanation
(a) [image:5_image194.emf]
According to conservation of linear momentum
$p_{3} = \sqrt{p_{1}^{2} + p_{2}^{2}}$
$\Rightarrow m\ \times 4 = \sqrt{(1 \times 12)^{2} + (2 \times 8)^{2}} = 20 \Rightarrow m = 5\ kg$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.