Question

3) 20
A bullets each of mass 200gm are fired with a velocity of 10 ms-1 into a block of mass 3 kg
4)22
at rest in quick succession. If the bullets are embedded in it, the block moves with a
velocity of
1) 10 ms
2) 20 ms
3) 2.5 ms
4) 2 ms!​

Answer 1

mass of bullet,m1= 200g

=200/1000 kg

= 0.2kg

now, velocity of bullet,v1=10m/s

so, momentum of bullet =0.2*10 kg.m/s ......(1)

now, mass of block gets embedded by bullet m2= 3 + 0.2 kg= 3.2kg

now, velocity of block+bullet, v2 =?

so, momentum of block +bullet= m2*v2= 3.2* v2kg. m/s ........(2)

now,according to law of conservation of momentum, the two momenta as given by equation (1) and 2 should be equal

so, m1*v1= m2*v2

or, 0.2*10=3.2*v2

and, v2 = 0.2*10/3.2=0.625