Question

A bomb of mass 5 kg explodes at rest into three pieces of masses in the ratio 1 : 1 : 3. The pieces with equal masses fly in mutually normal direction with speed of 21 ms^-1. Velocity of the third piece is

• A. 9.12 ms^-1
• B. 7.98 ms^-1
• C. 9.87 ms^-1
• D. 8.97 ms^-1

Answer 1

Answer: (C)

9.87 ms^-1

Answer 2

Resultant momentum of two pieces of equal masses is

p = $\sqrt{(21 \times 1)^{2} + (21 \times 1)^{2}}$ = 21$\sqrt{2}$kg ms^-1

From conservation of momentum 3V = 31$\sqrt{2}$

(where V is velocity of 3 kg piece)

or V = 7$\sqrt{2}$ = 9.87 kg m^-1