mass of bullet=10g=0.01kg
velocity of bullet=1.5ms
mass of plank=90g=0.09kg
Total momentum before collision=mass × velocity
=0.01×1.5+0.09×0=0.015kgms
Total momentum after collision=(mass of bullet +mass of plank )× velocity
=0.1kg×V=0.1Vkgms
According to law of conservation of momentum,
Total momentum before collision=Total momentum after collision
0.015kgms=0.1vkgms
velocity acquired by theplank and the bullet=0.15ms