# What Is Velocity

Kinematics of motion holds one section of Physics and velocity is an unprecedented part of kinematics. Velocity is nothing but a more detailed description of speed. When direction of motion is given along with the speed of  moving body then we get the concept of velocity. In everyday life, we generally use the term speed to associate the rate of change of distance of any moving object. However, direction of a moving object defines its displacement, which gives the trajectory of the moving object. Velocity offers the essential approach required in kinematics. Velocity is a vector quantity and can be expressed by the following relation:     v = s / t Here, v stands for velocity, s for displacement and t for time. The definition of velocity needs both magnitude and direction, where magnitude is a scalar quantity. This scalar magnitude is nothing but speed.

Uniform Velocity and Variable velocity If a moving body travels with an invariable speed without changing its direction even for a moment. Then the object is said to have uniform velocity. Otherwise, the velocity of the object is variable in nature. When an object travels with uniform velocity then it covers equal distance in equal interval of time. If we plot a graph where, displacement takes the y-axis and time takes the x-axis then we will get a straight diagonal line. The straight line is nothing but uniform velocity which is also the slope of s-t curve. Hence, a slope of a curve in a graph of displacement and time gives the velocity.  If the line is straight then it is uniform velocity otherwise variable velocity.

Acceleration In real life no moving object can move with uniform velocity. An object’s velocity changes with times and it is known as acceleration. Acceleration is defined as the rate of change in velocity of a moving object. The following expression explains the term acceleration:         a = v / tHere, a stands for acceleration, v for velocity and t for time. Instantaneous acceleration can be easily calculated by differentiating the above relation with respect to time.

Relative velocity There are many situations where we have to find the velocity of one object with respect to another object, which can be in the state of rest or motion. This is concept behind relative velocity. The concept of relative velocity is used to calculate the velocity of two trains on parallel tracks and in the calculation of time when the trains pass each other etc.   vA/B  =  rA/B / t Here, rA/B  stands for rate of change of position vector of object A with respect to object B.

Velocity Vs SpeedVelocity is a vector quantity whereas speed is a scalar quantity. Velocity includes the direction in which the object is moving but speed of any object doesn’t specify the direction. It is impossible to know the position of an object by just knowing it’s speed but if we know the velocity of an object then we can track it’s position.