Speed : Definition, Types, Unit
Why is the man walking on the road able to cover less distance in the same time compared to a car that is riding next to him? The reason is that the car travels at a greater speed compared to the man. Similarly, a fast runner covers a greater distance compared to a slow runner because the former has greater speed compared to the latter. Speed is a measure of how fast or how slow someone or something moves.
Table of contents
What is Speed?
Speed can be defined as the. A car moving with a greater speed would be able to reach its destination faster compared to another car that is moving at a slower speed. Mathematically,
Speed is a The unit of speed is
The ratio of
taken by it to cover that distance is called the average speed.
A moving body always possesses a
The slope of the graph gives aerage speed. Consider the following graph. If “ indicates displacement in time “t”,then between two points a and b,
The instantaneous speed of a particle can be defined as the speed of a particle at a particular .
i.e first derivative of s wrt time gives instantaneous speed.
Consider the following s-t graph which depicts a non-uniform motion. The , ie. the value of instantaneous speed at that point.
Let us take for example, three athletes A,B and C who are running a race on the same track, parallel to each other. Now athlete A runs the fastest ,B is faster than C, however slower than A.
Relative speed gives an idea how one body travels slower or faster in comparison to another. In this case, A moves at a greater speed compared to C, as A moves as compared to B.
The relative speed of A wrt B (when they are moving in the same direction) can be written as
When A and B run in opposite directions, relative speed of A wrt B is
Uniform and Non-uniform Motion
A motion is said to be uniform if the body covers equal distances in equal intervals of time. For eg. if a body covers 2 m of distance each second, the body is said to be in uniform motion. Whereas a motion is said to be non-uniform if the body covers unequal distances in equal intervals of time. A body in non-uniform motion is said to have acceleration.
Practice Problems of Speed
(a) 22 m/s (b) 44 m/s (c) 33 m/s (d) 11 m/s
The distance traveled along AB
be the times taken by the car to go from X to Y and from Y to X .
Since A and B run in opposite directions, relative speed= 2 m/s+1 m/s=3 m/s
(a) 10 m/s (b)12 m/s (c)5 m/s (d)24 m/s
Let the car travel distance d/2 taking time t1 and the next part taking time t2
FAQs of Speed
Speed is defined as the ratio of distance to the time taken. Speed is a scalar quantity. Velocity is displacement covered by an object divided by the time taken; and is a vector quantity.
Distance traveled is the length, so it’s unit is m, and unit of time is s. So, unit of speed is ms-1.
Let’s say a body moves from A to B along the semicircle. Now we can clearly see that distance is greater than the magnitude of displacement. Distance = magnitude of displacement for a straight line motion. So, average velocity can never be greater than average speed.
The speedometer shows the speed at a given time. So, the speedometer shows us instantaneous speed.