Assertion: The relative velocity of the two particles in head-on elastic collision is unchanged both in magnitude and direction.
Reason: The relative velocity is unchanged in magnitude but gets reversed in direction.

Give one example when the velocity of an object changes at a constant rate both in magnitude and direction.

Assertion: In projectile motion, the acceleration is constant in both magnitude and direction but the velocity changes in both magnitude and direction. Reason: When a force or accelration is acting in an oblique direction to the direction of velocity then both magnitude and direction of the velocity may be changed.

In a laminar flow at a given point the magnitude and direction of the velocity of the fluid

Assertion: Relative velocity of A w.r.t B is greater than the velocity of either, when they are moving in opposite directions. Reason: Relative velocity of A w.r.t B=vecv_(A)-vecv_(B)

Two objects A and B are moving along the directions as shown in (Fig. 5.77). Find the magnitude and direction of the relative velocity of B w.r.t. A . ,

Assertion : The accelerated motion of an object may be due to change in magnitude of velocity or direction of velocity or both. Reason : Acceleration can be produed only by change in the magnitude of the velocity.

Assertion: A physical quantity cannot be called as a vector if its magnitude is zero. Reason: A vector has both, magnitude and direction.