In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant while the vertical component changes?


How does the downward component of the motion of a projectile compare with the motion of free fall??

In a gravitational field? Because the gravitational force acts in the direction along the line between the centre of mass of both bodies.

There is no horizontal acceleration, that's why.

The only acceleration (negative) is due to gravity

The downward component is exactly like free fall - only difference is that there is still
Horizontal velocity along with this free fall.