Why Com Is an Important Point

Q. Calculate the reduced mass of $HCl$ molecule.
Given that the mass of $H$ atom is $1.0078\text{amu}$ and the mass of Cl atom is $34.9688\text{amu}$.
Note that $1\text{amu}=1.660565\times {10}^{-27}\text{kg}$.

1. $1.627\times {10}^{-27}\text{kg}$
2. $1.253\times {10}^{-27}\text{kg}$
3. $1.978\times {10}^{-27}\text{kg}$
4. $2.538\times {10}^{-27}\text{kg}$

Q. Two blocks of masses $3\text{kg}$and $6\text{kg}$ respectively are placed on a smooth horizontal surface. They are connected by a light spring of force constant $k=200\text{N/m}$. Initially the spring is unstretched. The indicated velocities are imparted to the blocks. Find the maximum extension of the spring.

1. $30\text{cm}$
2. $60\text{cm}$
3. $15\text{cm}$
4. $90\text{cm}$

Q. Seven identical geese are flying south together at constant speed. A hunter shoots one of them, which immediately dies and falls to the ground. The other six continue flying south at the original speed. After the one goose has hit the ground, the center of mass of all seven geese

1. Continues south at the original speed, but is now located some distance behind the flying geese.
2. Continues south, but at $\frac{6}{7}$ the original speed.
3. Continues south, but at $\frac{1}{7}$ the original speed.
4. Stops with the dead goose.

Q. Two objects are moving on a surface.The center of mass exists only if -

1. the two objects are physically connected
2. the surface is level
3. the surface is frictionless
4. There is always a center of mass.

Q. A uniform sphere is placed on a smooth horizontal surface and a horizontal force F is applied on it at a distance h above the surface. The acceleration of the center

1. Is Maximum when h=0
2. is maximum when h=R
3. is maximum when h=2R
4. is independent of h.

Q. The reduced mass of two particles having masses $4m$ and $2m$ is

1. $2m$
2. $3m$
3. $\frac{4m}{3}$
4. $\frac{m}{2}$