I dont understand how objects lose their velocity when for example they’re in air. Shouldnt the momentum of it be constant?
In: Physics
Don’t confuse velocity and acceleration. Velocity is speed and direction. Acceleration is a change in speed or direction. A force applied to an object is acceleration, so by definition, it changes the object’s speed and direction by speeding it up, slowing it down, or diverting it.
A cartridge accelerates a bullet when it ignites in the chamber and the gasses expand. This accelerates the bullet in the direction of the least opposing force, which is (hopefully) the barrel. But once the bullet leaves the barrel, this force is no longer acting on the bullet and is not accelerating it.
Other forces are still present, though, and they change its velocity. Gravity exerts a force that accelerates the bullet toward the gravitational center of the earth (sideways acceleration, direction). Air resistance exerts a force opposite to the bullet’s path (negative acceleration, speed) through the resisting medium.
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