Im having a hard time understanding momentum with people defining it in terms that don’t really explain what it is. I think that getting a feel of what the unit for momentum is might help me
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Before looking at Momentum lets look at what Velocity and Acceleration mean since it’ll help us.
Velocity is how fast something is going in a given direction. We define Velocity thus as displacement, not distance, divided by time. The SI unit for this would be Meters per Second. m/s, Acceleration is the measure of how much the Velocity changes over time. If you’ve studied calculus you’d recognize this as the derivative of Velocity. Acceleration is measured in the SI unit Meter per second squared, m/s^2
Thus we can move onto Force and Momentum. Momentum is how much mass is moving in a given direction in a given time. From this we can see that Momentum is defined as Velocity times Mass, or Kg*m/s. Force is how quickly a mass is accelerating, and is thus defined as Mass times Acceleration. These are not the same thing! If an object is moving, it does not necessarily have a force acting on it. Equally, an object could have a force acting on it, but not be moving. From this we can see that force is the change in momentum over time. Note we don’t generally refer to change in momentum as force, but rather the impulse as Force does not have a time component.
These can be a bit unintuitive so a quick look at them. If we launch a rocket into space, it will accelerate as long as its engines are burning. It will get faster and faster and faster, until we run out of fuel. The engine is applying a force to the rocket to make it move faster in a direction. Once the rocket engine cuts out, there is no longer any force acting on the rocket (assume its in a perfect vacuum far enough way from any mass for gravity to act upon it). The rocket however is still moving, and will continue to move in whatever direction it was flying at whatever final speed it had reached, forever. For the case of force with no motion, an example would be friction. If we attempt to push a heavy object, if the amount of force were applying to the object is less then the opposing force of friction, it won’t move.
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