Question

Bullet having a mass of 10 gram and moving with a speed of 1.5 metre per second penetrates a wooden plank of mass 90 gram the plank was initially at rest. the bullet gets embedded in the plank and plank and both move together.............
..?..........................................................
...............determine the velocity?and explain it.....

Answer 1

in this case you can apply law of conservation of momentum which is

Final momemtum=initial momentum

as if we take bullet and plank as a system then initially only bullet is moving with speed of 1.5 m/s and plank is in rest. so,

initial momentum= mass of bullet x velocity
= 0.01 x 1.5
= 15*10^-3
finally both are attached so new mass is 90+10= 100gram=0.1kg
then

0.1v= 0.015
v = 0.15 m/s