Highly selective Backlog Qs for JEE MainPhysicsCenter of Mass, Momentum and Collision
An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 ~kg moves with a speed of 12 ~ms ⁻¹ and the second part of mass 2 ~kg moves with 8 ~ms ⁻¹ speed. If the third part flies off with 4 ~ms ⁻¹ speed, then its mass is
Options
- A3 ~kg
- B5 ~kg
- C7 ~kg
- D17 ~kg
Correct answer
B. 5 ~kg
Step-by-step solution
We have p₁+p₂+p₃=0 [ p=m v] aligned & 1 12 i+2 8 j+p₃=0 & 12 i +16 j + p ₃=0 & P ₃=-(12 i +16 j ) & p ₃= (12)^2+(16)^2 & = 144+256 & =20 ~kg - m / s aligned Now, p₃=m₃ v₃ m₃= p₃ V₃ = 20 4 =5 ~kg