# Moment, Impulse, and Collisions

Momentum is the product of mass and velocity. It is often represented by the letter p. In SI units, the unit of momentum is the kilogram meter per second (kg m/s), the unit of force is the newton (N), and the unit of mass is the kilogram (kg). Momentum is a vector quantity, meaning that it has a magnitude and direction. If a system has a velocity and the direction of motion is not changing, its momentum will be constant. If a system has a velocity and the direction of motion is changing, the momentum will not necessarily be constant. Momentum is an important concept in physics, as it is a conserved quantity. That is, if a system has no external forces acting on it and it is moving at constant velocity, the total momentum of the system will not change with time. This is a consequence of Newton's first law, which states that in an isolated system, the net force acting on a body is equal to its mass times its acceleration. Momentum is also a conserved quantity in a system with friction, such as a car moving along a road. Friction is like an external force that slows the car. The momentum of the car will change, but it will not change in the direction of motion. Momentum is the product of mass and velocity, and is a scalar quantity, meaning that it has magnitude but not direction. A particle or body with momentum has mass multiplied by velocity. For example, a billiard ball is moving because it has momentum, and it has mass because it is not an ideal particle. The billiard ball has a velocity that is changing as it moves. If the velocity of the ball is not changing, its momentum is constant. The SI unit of momentum is the kilogram meter per second (kg m/s). One kilogram meter per second is equal to one meter per second. The momentum of a moving object is related to the force acting on it by the following equation: This force is called the impulse of the object, and is equal to the change in momentum of the object divided by the time that the momentum changes. If the force is constant in time, the impulse is equal to the change in momentum. In the equation above, "d" is the change in momentum, and "dt" is the time rate of change. In SI units, the unit of momentum is the kilogram meter per second (kg m/s), the unit of force is the newton (N), and the unit of mass is the kilogram (kg). Momentum is a scalar quantity, meaning that it has magnitude but not direction. Momentum is defined as a vector when the object is moving in a straight line. If an object changes its velocity, its momentum will change because of the force that is exerted on the object. When an object is moving with constant velocity, its momentum is constant. Therefore, if an object has a velocity of 0 m/s and the momentum is 0, the object will have a momentum of 0. A moving object of mass "m" will have a momentum of "p" = "m" · "v", where "v" is velocity. The SI unit of momentum is the kilogram meter per second (kg m/s). One kilogram meter per second is equal to one meter per second. The momentum of a moving object is related to the force acting on it by the following equation: This force is called the impulse of the object, and is equal to the change in momentum of the object divided by the time that the momentum changes. If the force is constant in time, the impulse is equal to the change in momentum. In the equation above, "d" is the change in momentum, and "dt" is the time rate of change. In SI units, the unit of momentum is the kilogram meter per second (kg m/s), the unit of force is the newton (N), and the unit of mass is the kilogram (kg). Momentum is a scalar quantity, meaning that it has magnitude but not direction. Momentum is defined as a vector when the object is moving in a straight line. If an object changes its velocity, its momentum will change because of the force that is exerted on the object. When an object is moving with constant velocity, its momentum is constant. Therefore, if an object has a velocity of 0 m/s and the momentum is 0, the object will have a momentum of 0. A moving object of mass "m" will have a momentum of "p" = "m" · "v", where "v" is velocity. The SI unit of momentum is the kilogram meter per second (kg m/s