Question

A shell at rest at the origin explodes into three fragments of masses 1 kg, 2 kg and m kg. The 1 kg and 2 kg pieces fly off with speeds of 5 ms^–1 along x-axis and 6ms^–1 along y-axis respectively. If the m kg piece flies off with a speed of 6.5 ms^–1, the total mass of the shell must be :

• A. 4 kg
• B. 5 kg
• C. 3.5 kg
• D. 4.5 kg

Answer 1

Answer: (B)

5 kg

Answer 2

P₃ = $\sqrt{P_{1}^{2} + P_{2}^{2}}$

m₃v₃ = $\sqrt{5^{2} + 12^{2}}$

or m₃v₃ = 13

or m₃ = $\frac{13}{6.5} = 2kg$

 Total mass = 1 + 2 + 2 = 5 kg