Question

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 thirds part files off with a velocity of $4\, ms ^{-1}$, its mass would be :

• A. 7 kg
• B. 17 kg
• C. 3 kg
• D. 5 kg

Answer 1

Answer: (D)

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 $12 \,m / s$ and $2 \,kg$ second part moving with a velocity of $8\, m / s$. If the thirds part files off with a velocity of $4 m /$ sits mass would be
$\vec{ P }_{1}+\vec{ P }_{2}+\vec{ P }_{3}=0$
$\left|\vec{ P }_{3}\right|=\left|\vec{ P }_{1}+\vec{ P }_{2}\right|$
$m \times 4=\sqrt{ P _{1}^{2}+ P _{2}^{2}}=\sqrt{12^{2}+16^{2}}=20$
$m * 4=20\, kg$
$m =5 \,kg$