Question

Two identical blocks A and B connected by a massless string are placed on a frictionless horizontal plane. A bullet having same mass moving with a speed u strikes block B from behind as shown. If the bullet gets embedded into the block B, then find the impulse on C due to normal force of collision?

• A. $\frac{-2mu}{3}$
• B. $\frac{2mu}{3}$
• C. $\frac{3mu}{3}$
• D. $\frac{-3mu}{3}$

Answer 1

The correct option is A $\frac{-2mu}{3}$

The impulse experienced by the object equals the change in momentum of the object.

Initial momentum of C $=mv$

Final momentum we have to find final velocity of the bullet,

Taking $A,BandC$ as one system

Conserving linear momentum $0+0+mv=3m{v}_1$

$v_1=\frac{v}{3}$

So final momentum of C $=\frac{mv}{3}$

Impulse experienced on C is $\frac{mv}{3}-mv$

$=-\frac{2mv}{3}$.