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 A due to tension in the string.

• A. $\frac{mu}{3}$
• B. $\frac{2mu}{3}$
• C. $\frac{m{u}^2}{3}$
• D. $\frac{mu}{2}$

Answer 1

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

Now apply momentum conservation we get
$m_1{u}_1$+$m_2{u}_2$=$m_1{v}_1$+$m_2{v}_2$
$mu$+0=0+$3mv$
$v=$$\frac{u}{3}$
We know that impulse is given by,
$J=F.t=m(v-u)$
where, $u=0$
So on substituting the value of "$v$" we get,
F=$\frac{mu}{3}$