Question

A 20 kg Block moving East at 30 ms collides with a 25 kg Block of rest. The two block stick together. What is the final speed of two Blocks ?​

Answer 1

Answer

Correct option is

B

800 Joule

As there is no external  non-conservative force on the system (both masses altogether) the linear momentum should

be conserved.

Thus we should have m  

1

​

v  

1

​

+m  

2

​

v  

2

​

=(m  

1

​

+m  

2

​

)V (inelastic collision)

V is the common velocity after the collision.

putting values we get 20(10)+5(0)=(20+5)V or V=8m/s

so the new KE will be K=  

2

1

​

mV  

2

=0.5×25×64=800Joule

Answer 2

Answer:

As there is no external non-conservative force on the system (both masses altogether) the linear momentum should

be conserved.

Thus we should have m

1

v

1

+m

2

v

2

=(m

1

+m

2

)V (inelastic collision)

V is the common velocity after the collision.

putting values we get 20(10)+5(0)=(20+5)V or V=8m/s

so the new KE will be K=

2

1

mV

2

=0.5×25×64=800Joule