Question

A radioactive particle at rest, having mass 10g, breaks into 2 fragments (1&2) in the mass ratio 2:3 respectively. If the first one moves with a velocity of 10m/s what will be the speed of the second particle?

(a) 4.33 m/s

(b) -4.33 m/s

(c) -6.67 m/s

(d) 6.67 m/s

The question was asked in an online interview.

Enquiry is from Linear Momentum of a System of Particles topic in portion System of Particles and Rotational Motion of Physics – Class 11

Answer 1

Correct option is (c) -6.67 m/s

Explanation: let the mass of part 1 be 2x, & the mass of part 2 be 3x since the masses are in the ratio 2:3.             2x + 3x = 10g.

∴ x = 2g. Therefore, masses of part 1 & 2 are 4g & 6g respectively.

The total momentum will be conserved because there is no external force.                                                               Let the velocity of 2nd part be ‘v’.

∴ 0 = 4*10 + 6*v                                                                                                                                                                                  ∴ v = -40/6 = -6.67 m/s.