Speed:
Speed is defined as the distance travelled by an object in unit time.
\(\text{Speed} = \frac{\text{Distance travelled}}{\text{time}}\)
SI unit of speed:
Speed is measured in the units of \(cm/s\) or \(m/min\) or even \(km/h\) since, \(\text{Speed} = \frac{\text{Distance travelled}}{\text{time}}\)
But the SI unit of distance is metre (\(m\)) and time is second (\(s\)).
Hence the SI unit of speed is metre/second, expressed as \(m/s\).
Important!
To convert the unit from \(m/s\) into \(km/h\), multiply the given speed value by \(18/5\).
To convert the unit from \(km/h\) into \(m/s\), multiply the given speed value by \(5/18\).
Speed or average speed is the total distance covered divided by the total time taken.
\(\text{Average speed} = \frac{\text{Total distance covered}}{\text{Total time taken}}\)
Actual speed is the distance travelled by a body at a particular instant of time.
Speedometer:
Odometer:
A speedometer is an instrument in vehicles that shows the speed at which the vehicle is moving at a particular moment. It is usually marked in kilometres per hour (\(km/h\)).
An odometer is an instrument in vehicles that measures the total distance the vehicle has travelled. It is usually displayed in kilometres (\(km\)).
Motion:
Motion is the change in the position of an object with respect to its surroundings over time.
Types of motion:
The objects that move along a straight line are in rectilinear motion or linear motion.
Example:
Motion of any vehicle on a straight road, soldiers in a parade, and runners in a \(100\)-metre race.
Circular motion:
The motion in which an objects move along a circular path is called circular motion.
Example:
Pedals of a bicycle, hands of a clock, and blades of a fan
Uniform motion:
An object is said to be in uniform motion if it travels in a straight line with a constant speed. Here, the object travels equal distances in equal intervals of time. So, the average speed is the same as the actual speed of an object.
Example:
The blades of the fan moves in a uniform circular motion with a constant speed in equal intervals of time.
Non-uniform motion:
An object is said to be in non-uniform motion if it travels along a straight line with a variation in speed. The object travels unequal distances in equal intervals of time. Here, the average speed is not the same as the actual speed of an object.
Example:
At the starting point of the journey, the train was at rest, and then it started moving slowly. After covering a certain distance, the train gathered some speed. Then, it slowed down while crossing a bridge and stopped at the stations for passengers. Finally, the train slowed down and came to a halt at the last station. Throughout the journey, the speed of the train was not the same. Thus, the motion is said to be non-uniform motion.