If an object changes its position with respect to time, it is said to be moving. A moving object is known to exhibit motion. Motion is a phenomenon that is very common in our daily life. For example, the car in which you travel moves, the air we breathe is in motion, the blood in our veins is in motion, the earth is in motion, the universe is moving and many more. Technically, even the stationary objects on our planet are in motion, the reason being that the earth is in constant motion itself, i.e., rotation and revolution.
Types of Motion
We can observe a lot of motion-related activities in our daily life. However, different moving things may differ in the manner with which they are moving. For instance, a playing swing exhibits the to-and-fro motion, while movement on a trampoline is up-and-down. Both of them are moving but differently. Based on this, we have different types of motion. Motion can be roughly classified into four categories, namely, linear, rotary, oscillating, and reciprocating.
Following are the different types of motions:
Translatory motion is the motion in which all particles of the object move the same distance at the same time. Rectilinear and Curvilinear motions are the subcategories of translational motion. For example, bowling, pulling a drawer, gunfire, etc.
Rectilinear motion, also known as linear motion, is said to be present if the object or the particle moves along a straight line. In other words, rectilinear motion is also known as straight-line motion. For example, children sliding down a slide, an apple falling from a tree, etc.
Curvilinear motion occurs when the object moves along a curved path. The notion of curvilinear motion is used in the applications that are related to centripetal and centrifugal forces. For example, boomerang, roller coaster, etc.
Circular motion or circulatory motion is the movement of objects along the circular path, which means along the path whose every boundary point is equidistant from a fixed point, i.e., centre. For example, the movement of planets around the sun, giant wheel, etc.
Rotatory motion is said to exist if the object rotates or spins about its axis. For example, spinning top, rotation of the earth and other planets, etc.
In oscillatory motion, an object tends to repeat certain movements in the same pattern again and again, until it is acted upon by some external force. In the absence of friction, the oscillatory motion has the ability to go on forever till eternity. For example, a pendulum, flapping of bird wings, etc.
Some objects display a rapid back and forth motion about a fixed point when their equilibrium condition is disrupted. This type of motion is known as vibratory motion. For example, guitar strings, vocal cords, etc.
The name itself suggests that the motion will be repeated after a certain period of time. The time taken to complete one cycle of the motion is called the period. For example, the movement of the hands of a clock, a rocking chair, etc.
Reciprocating motion and vibratory motion are very closely related to each other, but there is a small exception that reciprocating motion necessarily involves up-and-down or back-and-forth motion. For example, sewing machine needle, piston pumps, etc.
Brownian motion is the random motion of particles suspended in a medium. It is also known as pedesis. For example, the motion of water molecules, the movement of dust particles, etc.
Any motion which is an outcome of a mixture of any of the above-mentioned motions may be considered under the category of combination motion. For example, when you run with a pinwheel in your hand, the pinwheel shares linear motion with you and at the same time, it possesses rotational motion, as the wind pushes the fan to move around the pivot. Hence, due to the presence of two different types of motions, the body is known to exhibit multiple or combination motion.
Laws of Motion
The three laws of motion were brought to light by Sir Issac Newton. These three fundamental laws laid the foundation for other significant discoveries and achievements of the world we live in today. You must be very familiar with the Newton and the apple tree anecdote, it was after that incident that we were able to identify gravity as a natural phenomenon.
1. Newton’s First Law of Motion
It states that ‘an object tends to maintain its state of rest or state of motion unless acted upon by an external force.’ It is also known as the law of inertia.
2. Newton’s Second Law of Motion
It states that ‘the acceleration of an object is directly proportional to the net force exerted and inversely proportional to the object’s mass.’ Mathematically, F=m a; where F=force, m=mass, and a=acceleration.
3. Newton’s Third Law of Motion
It states that ‘for every action, there is an equal and opposite reaction’.
Examples of Motion
This is one of the most prominent examples of rectilinear motion. For example, it’s possible for children to slide freely on various slides only because there is the presence of gravity; moreover, while sliding, children also experience low friction; leading to an easy and smooth slide.
Boomerangs display one of the most captivating phenomena, it is way too exciting to see it return to the thrower after following a curved path. This curved motion segregates it into the category of curvilinear motion.
When a bowling ball is in motion, a linear relationship is established between the motion and the time. Therefore, every part of it experiences translational motion. The application of Newton’s First Law of Motion may also be observed here as the ball tends to move continuously along the lane until the motion gets disrupted by hitting the pins.
4. Planets around the sun
In the solar system, planets revolve around the sun in a fixed orbit, this sort of motion can be labelled under circulatory motion.
5. Spinning Top
We all have played with a spinning wheel as a child being unaware of the science behind it. A spinning top demonstrates typical rotational motion as the top keeps going round and round about its axis.
When a pendulum, hanging freely, is given a slight push, it changes its position from equilibrium to a certain distance on one side, returning again to the equilibrium, then moving the same distance on the other side, and so on. Such a pendulum is said to be oscillating, and such a motion is called oscillatory motion. One can relate Newton’s Second Law of Motion in this case. A pendulum with greater mass would require a greater force to bring it to swing, whereas a pendulum with lesser mass would require a lesser force. Hence, the force is proportional to mass. Similarly, the greater the mass of an object, the lesser will be its acceleration or vice versa. Therefore, acceleration is inversely proportional to the mass. Combining the two observations, we get, F=ma (second law of motion).
7. Guitar Strings
The sound that we hear from stringed instruments like guitar, sitar, etc. is a result of the vibratory motion of the strings. Here, the kinetic energy generated by vibration gets converted to sound energy. Newton’s Third Law of Motion can be clearly observed here, as the pressure applied on the strings is equal to the pressure exerted by the strings on the fingers of the player.
8. Ticking of Clock
The motion of the hands of a clock is repeated after a certain amount of time. Therefore, it exhibits a periodic motion. One major thing to observe here is that the motion of a clock is an example of compound motion too because while the hands of clocks exhibit periodic motion, they also go through the rotational motion.
9. Sewing Machine Needle
The needle of a sewing machine moves up and down in a repeated fashion. This up and down motion is responsible to put it under the group of reciprocating motion.
10. Molecules of Water
The water molecules are unpredictable as they do not follow any pattern while moving. This random and haphazard fluctuation of molecules is an example of pedesis or Brownian Motion.