Question

A body moves with uniform velocity, the velocity-time graph
A. makes a positive slope with time axis
B. is a straight line parallel to velocity axis
C. is a straight line parallel to time axis
D. is a curve

Answer 1

Hint: When the motion of a body is in such a way that it has equal displacements in equal intervals of time, the body is said to be in uniform velocity. Therefore, the velocity of the body is $\dfrac{s}{t}$ and this will be a constant value.

Complete step by step answer:
Velocity is defined as the change in position of a body in one unit of time or the displacement of the body in one unit of time.
Since velocity changes its position in one unit of time, it has a specific direction. Hence, it a vector quantity. The SI unit of velocity is $m{{s}^{-1}}$.
When the motion of a body is in such a way that it has equal displacements in equal intervals of time, the body is said to be in uniform velocity. And the velocity of the particle is simply the ratio of the displacement in the given time interval to the time interval.
Suppose a body is moving with a uniform velocity. Consider an interval of time t. Let the magnitude of displacement of the body the interval of time t be s. As per the definition of uniform velocity, for every time interval equal to t, the displacement of the body will be s. Therefore, the velocity of the body is $\dfrac{s}{t}$ and this will be a constant value.
Hence, we get that the velocity of a body moving with uniform velocity is constant with time.
Therefore, when we plot a graph of velocity versus time, we will get a straight line that is parallel to the axis of time.

Here, the y axis is the axis of velocity and x axis is the axis of time.
Hence, the correct option is C.

Note: Note that when a body is moving with a uniform velocity, it is moving in a straight line. This is because constant velocity means that the direction of motion is fixed.
Be careful while using the terms speed and velocity. Let us discuss the difference between speed and velocity. Speed the distance travelled by a body is one unit of time whereas velocity is the change in position (displacement) of the body in one unit time.
Speed does not have any specific direction but velocity does have a specific direction. Therefore, speed is a scalar quantity and velocity is a vector quantity.