Assertion: An object can have constant speed but variable velocity.
Reason: Speed is a scalar, but velocity is a vector quantity.

Assertion : In projectile motion, when horizontal range is $n$ times the maximum height, the angle of projection is given by $\tan \theta =\frac{4}{n}$

Reason : In the case of horizontal projection the vertical velocity increases with time.

Assertion : in projectile motion the projectile hits the ground with the same velocity with which it was thrown.

Reason : In projectile motion horizontal velocity remains same but vertical velocity continuously change and particle strikes the ground with same vertical velocity with which the particle was thrown in vertical direction.

Assertion: In projectile motion, the vertical velocity of the particle is continuously decreased during its ascending motion.

Reason: In projectile motion, downward constant acceleration is present in vertical direction.

Assertion : The path of one projectile as seen from another projectile is a straight line.

Reason : Two projectiles projected with same speed at angles $\alpha$ and $\left(90°-\alpha \right)$ have same range.

Assertion: In the projectile motion, projected body behave just like a freely falling body.

Reason: There is no change in linear momentum in projectile motion.

Assertion : Projectile motion is uniformly accelerated motion. (Neglect the effect of air.)

Reason : In projectile motion, speed remain constant

Assertion : Horizontal range is same for angle projection $\theta$ and $\left(90°-\theta \right),$ if speed of projectile is same.

Reason : Horizontal range is independent of angle of projection.