KINEMATICS - SPEED AND VELOCITY

KINEMATICS - SPEED AND VELOCITY
Speed:
Speed is the distance travelled per unit of time. 
It is how fast an object is moving. 
Speed is the scalar quantity that is the magnitude of the velocity vector. It doesn’t have a direction. Higher speed means an object is moving faster. Lower speed means it is moving slower. If it isn’t moving at all, it has zero speed. 
    The most common way to calculate the constant velocity of an object moving in a straight line is the formula:
                        S = d / t
where,
    S is the speed (sometimes denoted as v, for velocity)
    d is the distance moved
    t is the time it takes to complete the movement.
Units for Speed:
    The SI units for speed are m/s (metre per second). In everyday usage, kilometre per hour or miles per hour are the common units of speed. At sea, knots (or nautical miles per hour) is a common speed.
Types of speed:
There are four types of speed and they are:
    1. Uniform speed        2. Non-Uniform speed
    3. Average speed        4. Instantaneous speed
Uniform speed: 
An object is said to be in uniform speed when the object covers equal distance in equal time intervals.
Ex: Movement of blades of a ceiling fan.
Non-Uniform speed: 
An object is said to be in non-uniform speed when the object covers a different distance in equal intervals of times.
Ex:  The motion of a train.
Average speed: 
    Average speed is defined as the uniform speed which is given by the ratioof total distance travelled by an object to the total time taken by the object.
    The average speed of a body in a certain time interval is the distance covered by the body in that time interval divided by time. So, if a particle covers a certain distance s in a time t₁ to t₂, then the average speed of the body is:
            \({V_{avg}} = \frac{S}{{{t_2} - {t_1}}}\)
    In general, average speed formula is:
\(Average\,\,Speed\,\, = \frac{{Total\,\,Distance}}{{Total\,time}}\)
Instantaneous speed: 
    When an object is moving with variable speed, then the speed of that object at any instant of time is known as instantaneous speed.
    The average velocity tells us how fast an object has been moving over a given time interval but does not tell us how fast it moves at different instants of time during that interval. For this, we define instantaneous speed. It is the rate of change of distance with respect to time.
    Instantaneous speed is always greater than or equal to zero and is a scalar quantity. For uniform motion, instantaneous speed is constant. To understand it in simple words we can say that instantaneous speed at any given time is the magnitude of instantaneous velocity at that time. It is a limit of the average speed as the time interval become very small.
    A moving object does not have the same speed during its travel. Sometimes it speeds up and sometimes slows down. At a given instant time what we read from the speedometer is instantaneous speed. When a cop pulls you over for speeding, he clocked your car’s instantaneous speed or speed at a specific point in time as your car sped down the road.
Unit of Instantaneous Speed:
The SI unit of instantaneous speed m/s. It is a scalar quantity.