Two particles P and Q initially at rest are 1 m apart. P has a mass of 0.1 kg and Q has a mass of 0.3 kg, P and Q attract each other with a constant force of `10^(-2)N`. No external forces act on the system. At what distance from P's original position do the particles collide and the time taken by the particle for collision is

Options

A. 0.25 m, 3 sec
B. 0.75 m, `sqrt(15)` sec
C. 0.75 m, 3 sec
D. 0.25 m, `sqrt(15)` sec

Answer

B

Explanation

Two particles collide at their centre of mass.
`therefore` Distance of CM from `P=(0.1 times+0.3 times 1)/(0.1+0.3)=0.75m`
Consider `p:s_(1)=1/2a_(1)t^(2)" or "0.75=1/2""F/m_(1)t_(2)=1/2 times 10^(-2)/(0.1) times t^(2)" "therefore t=sqrt(15)sec`