10. The velocity of a projectile equals its initial velocity added to:
A. a constant horizontal velocity
B. a constant vertical velocity
C. a constantly increasing horizontal velocity
D. a constantly increasing downward velocity
E. a constant velocity directed at the target
Projectiles may be launched in two ways: i) from the ground, upwards at an angle and ii) from a height, horizontally. When launched from ground, upwards, the vertical velocity first decreases, comes to zero, then increases till it hits the ground. In type ii) projectile, the vertical motion is one of constant downward acceleration.The horizontal component of motion remains constant throughout, in both the cases.
The motion referred to in this problem is one of constant increase. therefore, it is a case of type ii) projectile discussed above. Therefore, the velocity of a projectile equals its initial velocity added to a constantly increasing downward velocity.
The correct answer therefore is option D).