Collisions between objects are governed by laws of momentum and energy. When a collision occurs in an isolated system, the total momentum of the system of objects is conserved. The total system kinetic energy before the collision equals the total system kinetic energy after the collision.

The vertical component of the momentum is not conserved, because the net vertical force Fy–net is not zero. In the vertical direction, the space probe-Earth system needs to be considered and we find that the total momentum is conserved.

Whether it is a collision or an explosion, if it occurs in an isolated system, then each object involved encounters the same impulse to cause the same momentum change. The impulse and momentum change on each object are equal in magnitude and opposite in direction. Thus, the total system momentum is conserved.

Explosions occur when energy is transformed from one kind e.g. chemical potential energy to another e.g. heat energy or kinetic energy extremely quickly. So, like in inelastic collisions, total kinetic energy is not conserved in explosions.

Generally, momentum is conserved in all types of collisions. There are four classes of collisions based on what happens during the collision and, in particular, what happens to the total kinetic energy of the system.

Collisions are of three types:

• perfectly elastic collision.
• inelastic collision.
• perfectly inelastic collision.

Newton’s third law of motion is naturally applied to collisions between two objects. In a collision between two objects, both objects experience forces that are equal in magnitude and opposite in direction. Such forces often cause one object to speed up (gain momentum) and the other object to slow down (lose momentum).

When two objects collide the total momentum before the collision is equal to the total momentum after the collision (in the absence of external forces). This is the law of conservation of momentum.

The definition of acceleration is: Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.

Total momentum is always conserved between any two objects involved in a collision. When a moving object collides with a stationary object of identical mass, the stationary object encounters the greater collision force.

Two objects with the same mass will always have the same momentum. Direction does not matter when you are measuring momentum. T 8. Momentum can be transferred from one object to another.