Question

A bullet of mass 10g when fired with a velocity of 20m/s strikes a block of mass 1kg
and gets embedded into it. Find the combined velocity of bullet and block.

Answer 1

Answer:

ExplanGiven :         m  

1

​  

=0.1kg             m  

2

​  

=2kg          u  

1

​  

=500   ms  

−1

          u  

2

​  

=0

Let the velocities of the bullet and the block just after the collision be  v  

1

​  

  and   v  

2

​  

   respectively.

The height upto which the block is raised  h=2  m

∴   From work-energy theorem for the block,                

2

1

​  

m  

2

​  

v  

2

2

​  

=m  

2

​  

gh

⟹v  

2

​  

=  

2gh

​  

 

v=  

2×10×2

​  

=2  

10

​  

    ms  

−1

 

Applying conservation of momentum just before and just after the collision :

m  

1

​  

u  

1

​  

+0=m  

1

​  

v  

1

​  

+m  

2

​  

v  

2

​  

 

0.1(500)=0.1v  

1

​  

+(2)×2  

10

​  

 

⟹v  

1

​  

=373.51        ms  

−1ation: