As we all know, motion means movement. The motion or movement is one of the vital signs of life in an organism. For example, animals and humans can move their body parts or they can move from one place to another without any external help.
After knowing about what is motion, distance and displacement in the previous post, we are going to discuss about the types of motion. There are two types of motion; one is uniform motion and another is non uniform motion.
So first come to uniform motion-
Uniform Motion
When an object travels equal distances in equal intervals of time, howsoever small the interval may be, the motion is said to be uniform.
For example, suppose a car covers 60 km in first hour, another 60 km in second hour, again 60 km in the third hour and so on. The motion of the car is uniform motion. Let us now understand the meaning of the words, 'howsoever small the time intervalmay be' used in the definition. In the above example, the car travels a distance of 60 km in each hour. In the stricter sense, the car should travel 30 km in each half hour; 15 km in every 15 minutes; 10 km in every 10 minutes, 5 km in every 5 minutes and 1 km in every one minute. Only then, the motion of the car is taken as uniform when it covers a distance of mind even when time interval is big. The motion of the car is taken as uniform when it covers a distance of 60 km in every one hour.
Then come to non uniform motion-
Non uniform Motion
When an object travels unequal distances in equal intervals of time, howsoever small the interval may be, the motion of the object is said to be non uniform.
For example, suppose a car covers 40 km in first hour, 50 km in second hour, 30 km in third hour, 70 km in fourth hour and so on, the motion of the car is non uniform, as it covers unequal distances in equal intervals of time.
After knowing about the types of motion, we have to discuss about the rate of motion.
The rate of motion is nothing but the speed.
It is defined as the distance travelled by the body in unit time.
Speed = distance travelled/time taken
If s is the distance travelled by a body in time t, its speed v is -
As SI unit of distance is metre (m) and that of time is second (s), therefore, SI unit of speed is metre/second. It is written as m/s or ms power -1.
Note:- The speed of a body is a scalar quantity. It has magnitude only. Speed of a body gives us no idea about the direction of motion of the body. The speed can be zero or positive. It can never be negative.
Then what are the types of speed?
1. Uniform Speed
2. Non uniform Speed or variable speed
When a body travels equal distances in equal intervals of time, howsoever small the intervals may be, the speed of the body is said to be uniform.
And when a body covers unequal distances in equal intervals of time, howsoever small the intervals may be, the speed of the body is said to be non uniform or variable.
In most cases, bodies move with variable speed or non-uniform speed. Therefore, we describe the rate of motion of such bodies in terms of their average speed.
The average speed of a body is obtained by dividing the total distance travelled by the total time taken,
i.e., average speed = total distance travelled/ total time taken.
After knowing about the types of motion and the defination of speed in the previous post, Today we have to discuss about the direction of motion of the body.
The rate of motion of a body will be more comprehensive if we specify the direction of motion alongwith its speed. The quantity that specifies both the rate of motion and direction of rate of motion is called velocity of the body.
Velocity of a body is the distance travelled by the body in unit time in a given direction.
In other words,
Velocity of a body is the speed of the body in a particular direction.
Thus, Velocity = distance travelled in given direction/time taken
Or Velocity = Displacement/Time
(where u is the intial velocity, v is the final velocity and Vav is the average velocity of the body).
Then difference between Speed and Velocity is -
Non living things cannot move on their own. We have to apply some external force to move them. For example, a scooter, a car, a bus and a truck move on the road when force is applied on them by their engines.
Motion
The motion of an object is perceived when its position changes continuously with respect to some stationary object.
What is the main difference between Mechanics and Kinematics?
- Mechanics deal with the motion of non-living objects as like as Kinematics. But Kinematics deal with the motion without taking into account the cause of their motion.
An object may appear to be moving to one person and the same object may appear to be at rest to another person.
For example- when a bus is moving on a road,
1. the roadside trees appear to be moving backwards to the passengers,
2. A person standing on the road finds the bus and the passengers moving forward,
3. A person inside the moving bus finds his fellow passengers at rest.
Thus, the states of rest and motion are relative only.
In order to describe the position of an object, we have to specify or choose a reference point which is known as Origin.
Assume that two points are given,
Then how many possible ways can be created to go from A to B or from B to A.
You know it well that it is infinite.
But what will be the shortest between them?
There is no logic behind it, Only you have to think properly.
That is the direct length between A and B means the straight line lies between the two points.
So, The shortest distance between two points is considered as Displacement.
Suppose we start our journey from point A and reach at point B. Then the length of the direct distance between the two points is Displacement But If we again go back to Point A. Then Displacement is equal to 0 because we start our journey from point A and ends in point A.
Now you have to carefully observed about this situation,
That the Displacement is completely dependent on direction and it has also magnitude. Therefore, we consider Displacement as a vector quantity.
Then what is distance?
Suppose an object starts its journey from a point along a straight line. Assume that there is three other points lies on it like A, B, C.
If it reached at point C and again it returns to point B.
Then the distance will be the sum of length between the intial point and the point C and the length between the Point B and C.
So The distance travelled by an object is the length of the actual path traversed by the object during motion.
As it doesnot depends on the direction, so we consider distance as scalar quantity.
Remember:- During the motion of the object, the value of distance can never be zero or negative.
Difference between Displacement and Distance is given below:-
After knowing about what is motion, distance and displacement in the previous post, we are going to discuss about the types of motion. There are two types of motion; one is uniform motion and another is non uniform motion.
So first come to uniform motion-
Uniform Motion
When an object travels equal distances in equal intervals of time, howsoever small the interval may be, the motion is said to be uniform.
For example, suppose a car covers 60 km in first hour, another 60 km in second hour, again 60 km in the third hour and so on. The motion of the car is uniform motion. Let us now understand the meaning of the words, 'howsoever small the time intervalmay be' used in the definition. In the above example, the car travels a distance of 60 km in each hour. In the stricter sense, the car should travel 30 km in each half hour; 15 km in every 15 minutes; 10 km in every 10 minutes, 5 km in every 5 minutes and 1 km in every one minute. Only then, the motion of the car is taken as uniform when it covers a distance of mind even when time interval is big. The motion of the car is taken as uniform when it covers a distance of 60 km in every one hour.
Then come to non uniform motion-
Non uniform Motion
When an object travels unequal distances in equal intervals of time, howsoever small the interval may be, the motion of the object is said to be non uniform.
For example, suppose a car covers 40 km in first hour, 50 km in second hour, 30 km in third hour, 70 km in fourth hour and so on, the motion of the car is non uniform, as it covers unequal distances in equal intervals of time.
After knowing about the types of motion, we have to discuss about the rate of motion.
The rate of motion is nothing but the speed.
It is defined as the distance travelled by the body in unit time.
Speed = distance travelled/time taken
If s is the distance travelled by a body in time t, its speed v is -
As SI unit of distance is metre (m) and that of time is second (s), therefore, SI unit of speed is metre/second. It is written as m/s or ms power -1.
Note:- The speed of a body is a scalar quantity. It has magnitude only. Speed of a body gives us no idea about the direction of motion of the body. The speed can be zero or positive. It can never be negative.
Then what are the types of speed?
1. Uniform Speed
2. Non uniform Speed or variable speed
When a body travels equal distances in equal intervals of time, howsoever small the intervals may be, the speed of the body is said to be uniform.
And when a body covers unequal distances in equal intervals of time, howsoever small the intervals may be, the speed of the body is said to be non uniform or variable.
In most cases, bodies move with variable speed or non-uniform speed. Therefore, we describe the rate of motion of such bodies in terms of their average speed.
The average speed of a body is obtained by dividing the total distance travelled by the total time taken,
i.e., average speed = total distance travelled/ total time taken.
After knowing about the types of motion and the defination of speed in the previous post, Today we have to discuss about the direction of motion of the body.
The rate of motion of a body will be more comprehensive if we specify the direction of motion alongwith its speed. The quantity that specifies both the rate of motion and direction of rate of motion is called velocity of the body.
Velocity of a body is the distance travelled by the body in unit time in a given direction.
In other words,
Velocity of a body is the speed of the body in a particular direction.
Thus, Velocity = distance travelled in given direction/time taken
Or Velocity = Displacement/Time
Where v is velocity and s is displacement of the body in time t.
The unit of velocity is the same as that of speed, i.e, metre/second, represented by the same symbol (v).
Remember:- Velocity is a vector quantity whereas speed is a scalar quantity.
Then what are the types of velocity?
1. Uniform Velocity
2. VariableVelocity
Uniform Velocity (constant velocity)
When a body is moving along a straight line, covering equal distances in equal intervals of time, howsoever small the interval may be, the velocity of the body is said to be uniform or constant.
For example -
When a train travels over a straight horizontal track covering 60 km in every hour, the train is said to have uniform velocity of 60 km/h.
Variable Velocity (or non uniform velocity)
The velocity of a body can be changed in any one of the following three ways:-
(i) By changing the speed of the body.
(ii) By changing the direction of motion of the body.
(iii) By changing both, the speed and direction of motion.
Thus,
Velocity of a body is said to be variable (or non uniform) when it covers unequal distances in a particular direction in equal intervals of time or the direction of motion of the body changes even when it covers equal distances in equal intervals of time.
Then come to average velocity -
Average Velocity
When a body is moving along a straight line at a variable speed, its velocity is variable. In that case, we express the rate of motion of the body in terms of its average velocity.
When velocity ofa body is changing at a uniform rate over a period of time, then average velocity of the body for this period is arithmetic mean of intial velocity and final velocity of the body.
i.e, average velocity = intial velocity + final velocity
2
Or
Then difference between Speed and Velocity is -
After knowing about the concept of velocity, we have to discuss about the rate of change of velocity.
When a body is moving uniformly along a straight line, its velocity is constant. Therefore, change in its velocity is zero, over any interval of time. However, when a body is in non uniform motion, its velocity changes, i.e, velocity of the body is different at different points of the path and at different instants of time. Thus, the change in velocity of the body is not zero, during any interval of time. To express the rate of change of velocity, we introduce another physical quantity, called acceleration.
Acceleration of a body is defined as the rate of change of velocity of the body with time. Thus, acceleration of a body is a measure of change in velocity of the body per unit time.
Thus,
Acceleration = change in velocity
time taken
As, change in velocity = Final velocity - Intial velocity
Acceleration = Final velocity - Intial velocity
time taken
Suppose u = intial velocity of a body at time t = 0
v = final velocity of the body at time t
a = acceleration of the body
Then a = v-u/t
Unit of acceleration
As acceleration is equal to change in velocity/time taken, therefore,
Unit of acceleration = unit of change in velocity/unit of time = metre/second
second
= metre/second × second
If the motion is along a straight line and the velocity of the body is increasing with time, the acceleration is in the direction of the velocity. Thus, acceleration is a vector quantity. The value of acceleration may be zero, positive or negative as disscussed below:
(i) when a body is moving along a straight line with a uniform velocity, change in its velocity (v-u) = 0. Therefore, acceleration, a = v-u/t = 0.
(ii) when the velocity of a body increases with time v > u. Therefore, (v-u) is positive and as such
a = v-u/t = positive
(iii) when the velocity of a body decreases with me, v < u. Therefore, (v-u) is negative and as such
a = v-u/t = negative
Remember: The negative acceleration is called retardation.
The negative acceleration (or retardation) is in a direction opposite to the direction of velocity of the body. For example, when a body is thrown vertically upwards, its velocity goes on decreasing due to opposing gravity. The acceleration is negative. Similarly, when we apply brakes, the vehicle slows down due to negative acceleration or retardation.
Then what are the types of acceleration?
1. Uniform Acceleration
2. Non uniform Acceleration
Uniform Acceleration
The acceleration of a body is said to be uniform, when velocity of the body moving along a straight line changes by equal amounts in equal intervals of time,i.e., when velocity of a body changes at a uniform rate, it is said to have uniform acceleration.
For example-
(i) motion of a body falling freely under the action of gravity,
(ii) motion of a ball rolling down a smooth inclined plane,
(iii) motion of a bicycle going down the slope of a smooth road when there is no pedalling and air resistance is neglected.
Non uniform Acceleration
When the velocity of a body changes at a non uniform rate,i.e, velocity changes by unequal amounts in equal intervals of time, the acceleration of the body is said to be variable or non uniform.
If you have still any doubt, Then feel free comment us.