A bullet of mass 15g is horizontally fried with a velocity 100ms_1 from a pistol of mass 2kg . what is the recoil velocity of the pistol

Dear student,

According to the law of conservation of momentum.
Initial momentum=final momentum
2 kg = 2000 g
M1 x V1 = M2 x V2
Therefore, 15 x 100 = 2000 x V2
V2 = 1500/2000=3/4=0.75 m/s
But it is in opposite direction, therefore, it will be negative.
Therefore,
recoil velocity = -0.75 m/s.

Regards