Momentum (p) can be defined and calculated using the following equation:
Where m is the mass and v is the velocity of an object.
The SI units for mass are kg and for velocity are ms-1. Therefore, the SI units for momentum are kg ms-1.
Momentum, like velocity, is a vector quantity. So as well as having magnitude it also has direction. The momentum of an object will be in the direction it is travelling.
The Conservation of Momentum
The conservation of momentum states that:
In a closed system the the total momentum before an event is equal to the total momentum afterwards.
A closed system is a system where there is no net change to the energy in the system (the total energy remains constant). This means that nothing can enter or leave the system.
Momentum is conserved during collisions and explosions.
Worked Examples
Example 1
A car of mass 1500kg travels along a road at 15ms-1. Calculate the momentum of the car.
Example 2
A ball of mass 0.4kg has a momentum of 3.6kg ms-1. Calculate the velocity of the ball.
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