Question

An explosion blows a rock into three parts Two parts go off at right angles to each other. These two are, $1kg$ first part moving with a velocity of $12m{s}^{-1}$ and $2kg$ second part moving with a velocity of $8m{s}^{-1}$. If the thirds part files off with a velocity of $4m{s}^{-1}$, 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, $1kg$ first part moving with a velocity of $12m/s$ and $2kg$ second part moving with a velocity of $8m/s$. If the thirds part files off with a velocity of $4m/$ sits mass would be
${\vec{P}}_1+{\vec{P}}_2+{\vec{P}}_3=0$
$\left|{\vec{P}}_3\right|=\left|{\vec{P}}_1+{\vec{P}}_2\right|$
$m\times 4=\sqrt{P_1^2+P_2^2}=\sqrt{12^2+16^2}=20$
$m\ast 4=20kg$
$m=5kg$