Question

which component of velocity of a projectile remains constant throughout time of flight

Answer 1

The horizontal velocity of a projectile is constant (a never changing in value), There is a vertical acceleration caused by gravity; its value is 9.8 m/s/s, down, The vertical velocity of a projectilechanges by 9.8 m/s each second, The horizontal motion of a projectile isindependent of its vertical motion.

Answer 2

YOOOO

DURING THE FLIGHT. X COMPONENT OF VELOCITY REMAINS CONSTANT.
i.e vcostheta component in X direction .