Question

in free space a rifle of mass M suits a bullet of mass m at a stationary block of mass M at a distance D from it when the bullet has moved through a distance d towards the block the centre of mass of the bullet-block system is at a distance of -

(1) (D-d)/M+m
(2) md + MD/ M+m
(3) 2md + MD/ M+m
(4) (D-d)M/ M+m​

Answer 1

Answer:

Momentum of system is conserb after fire. If bullet move of d then rifle move distance x back x=

M

m

d

Center of mass at (X_com) rifle =

M+M+m

M×0+m(d+x)+M(D+x)

X

com

=

2M+m

mx+md+Mx+MD

=

2M+m

Md+md+

m

M

2

d+MD

x=

m

M

d

=

2M+m

d(M+m+

m

M

2

)+MD