Why Com Is an Important Point

Q. An iron sphere of one kg is moving a velocity of 20m/son a cemented floor. It comes to rest after traveling a distance of 50m.Find the force of friction between the sphere and the floor.

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. Stops with the dead goose.
4. Continues south, but at $\frac{1}{7}$ the original speed.

Q. A man of mass M stands at one end of a plank of length L which lies at rest on frictionless surface. The man walks on the other end of plank. If mass of plank is M/3 the distance man moves relative to the ground is L/4

Q. What is the final velocity (v) and initial velocity (u) during each of these following situations: ( Please don't consider the gravitational force or the air)
​​​​​​1) A ball thrown vertically upwards at velocity of 6 m/s.
2) A ball thrown downwards at a velocity of 7 m/s.
3) A ball going vertically accelerating 4m/s.
4) A balloon which is in the air and releases a stone which takes a velocity 8 m/s to reach the ground ( find the u and v of the stone)

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

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.