Question

An object is moving with variable speed, then its velocity will be
(A) Zero
(B) Constant
(C) Variable
(D) None of the above

Answer 1

Velocity is the combination of direction and magnitude of speed at a particular instant. As an object is moving with variable speed it velocity will depend on the speed accordingly, as both are related at an instant.

Complete answer:
As per the problem an object is moving with a variable speed and we need to say what will happen to the velocity of that object.
Velocity:
The velocity of an object is defined as the rate of change of its position with respect to a frame of reference and is a function of time and it is a vector quantity as it has both magnitude and direction.
Speed:
Speed is defined as the rate at which an object covers distance. This means an object moving at higher speed can cover a larger distance while a slow moving object will cover a smaller distance. It is scale as it has only magnitude.
As in this problem we are only talking about the magnitude of speed which is variable.
Relation between speed and distance is:
$\dfrac{v}{s} = \dfrac{d}{D}$
Where,
Velocity = v
Speed = s
Displacement = d
Distance = D
Hence from all this discussion we can conclude that the change in speed or variable speed will show a change in velocity of the object or we can say that the velocity will vary.
Therefore the correct option is (C).

Note:
Here the velocity means we are talking about instantaneous velocity at a particular instant of time. Also remember that acceleration cannot be zero as the magnitude of velocity is changing as the acceleration is defined as the change in velocity by time.