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Finding the momentum of an object is easy if you know the mass of the object and its velocity.  The momentum of an object is a vector quantity that depends on the mass and the velocity of the object.  Since we already used the letter m for mass, we use the letter p to represent the momentum.

## Finding the Momentum of an Object

To find the momentum, simply multiply the mass times the velocity.

$$\color{black}{ \vec{p} = m \vec{v}}$$

Note that this is a vector equation. The mass is a scalar.  When we multiply it by the velocity (a vector) the result is a vector quantity.

Since momentum is a vector quantity, it can be broken into components.  As always, we usually choose our coordinate system in a way that simplifies the problem.  If you have an object moving in a straight line, you usually choose that direction to be the x-direction. Finding the momentum of an object involves multiplying the mass and velocity. The sign of the velocity determines the sign of the momentum. A stationary object has no momentum because its velocity is zero. An object moving to the left has negative momentum because its velocity is negative.

## Units of momentum

We simply multiply the mass and velocity of an object to find the momentum.  This means that the units for momentum contain a mass unit and a velocity unit.  If you are measuring in standard SI units, the units for momentum would be kg m/s.

There is no special name or symbol for this unit.  Make sure that you don’t accidentally square the seconds.  That would turn the combination into a newton.  Remember, Newtons measure force.

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