To replace a ball with another ball by collision, a snooker player must consider the condition that

In physics, momentum is the product of an object's mass and velocity, and is represented by the vector quantity p = mv. The equation for momentum is momentum = mass (m) x velocity (v). The unit of measurement for momentum is kilograms meter per second, or newton-second.  Momentum is directly proportional to an object's mass and velocity. For example, a truck with a lot of cargo has a lot of momentum and is difficult to stop at a stop light. A moving bullet also has a lot of momentum because it has a high velocity but a small mass.  Momentum can also be defined as force (F) = change in... Show more

In physics, momentum is the product of an object's mass and velocity, and is represented by the vector quantity p = mv. The equation for momentum is momentum = mass (m) x velocity (v). The unit of measurement for momentum is kilograms meter per second, or newton-second. 

Momentum is directly proportional to an object's mass and velocity. For example, a truck with a lot of cargo has a lot of momentum and is difficult to stop at a stop light. A moving bullet also has a lot of momentum because it has a high velocity but a small mass. 
Momentum can also be defined as force (F) = change in momentum (ΔP) over change in time (Δt). The change in momentum (ΔP) is also equal to the impulse (J), which has the same units as momentum (kgm/s or Ns). The effect of a force applied over a long period of time is the impulse of the force. 

Momentum is conserved in any inertial frame, and in special relativity, electrodynamics, quantum mechanics, quantum field theory, and general relativity. 

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