Table of Contents

## What happens to center of mass in elastic collision?

If you stand at the center of mass to observe an elastic collision, you see mass m1 approach with velocity V1(not the earth-frame-of-reference velocity v1 above), and mass m2 approaching with velocity V2. The masses collide at the center of mass (Ouch!). To do this, simply subtract vcm from each particle’s velocity.

**Is momentum conserved in center of mass frame?**

The total momentum is always zero in the center of mass reference frame.

### Does center of mass change in elastic collision?

The velocity of the system’s center of mass does not change, as long as the system is closed. The system moves as if all the mass is concentrated at a single point. The final location will be at the weighted distance between the masses.

**What is lab frame and Centre of mass frame?**

Remember that the centre of mass frame is just the frame in which we are travelling along with the centre of mass. This means that all we have to do to go from lab frame to CM frame velocities is subtract the velocity of the centre of mass.

#### What is the relationship between momentum and Centre of mass?

The linear momentum of a system of particles is equal to the product of the total mass M of the system and the velocity of the center of mass.

**How does center of mass move?**

If we push on a rigid object at its center of mass, then the object will always move as if it is a point mass. It will not rotate about any axis, regardless of its actual shape. If the object is subjected to an unbalanced force at some other point, then it will begin rotating about the center of mass.

## What role does center of mass play in conservation of momentum?

The fact that momentum is conserved only if the net force on the system is zero has a rather interesting implication. It turns out that it is the center of mass of the system that obeys Newton’s First Law. The location of the center of mass of a system can be thought of as the balancing point of the system.

**What quantities are conserved in elastic collisions?**

Elastic collisions are collisions in which both momentum and kinetic energy are conserved. The total system kinetic energy before the collision equals the total system kinetic energy after the collision. If total kinetic energy is not conserved, then the collision is referred to as an inelastic collision.

### How does center of mass change in a collision?

Center of Mass and Collisions in One Dimension Any force applied to a center of mass (or along a line that passes through the center of mass) will move the object from its current position. Any off-center force will cause an object to rotate around an axis, rather then move it from its point of origin..

**What do you mean by centre of mass frame?**

A frame of reference carried by the centre of mass of an isolated system of particles (i.e a system not subjected to any external forces) is called centre of mass frame of reference. In this frame of reference. (i) Position vector of centre of mass is zero.

#### What do you mean by center of mass frame?

A special case of the center-of-momentum frame is the center-of-mass frame: an inertial frame in which the center of mass (which is a physical point) remains at the origin. In all COM frames, the center of mass is at rest, but it is not necessarily at the origin of the coordinate system.

**What is the momentum of the center of mass?**

is the velocity of the center of mass. times the velocity of the center-of-mass.