# Fundamentals of Rest and Motion in Physics

Rohan Mathew

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Introduction To Equations Of Motion

In our daily lives, many things are moving around us, and many are not. When you are going from point A to point B, you are in motion, and when you finally reach point B and stop, you are at rest. At the most basic level, an object is at rest when its velocity is zero and in motion when its velocity is more than zero.

Let’s look at the equations of motion.

REST

An object is said to be at rest if it does not change its position with respect to its surroundings with time.

If you look around your room, you can see some objects are not moving. Your bed is in its place, cupboard, computer, study table, and many other objects. According to Newton’s 1st Law of motion,

An object at rest will stay at rest unless acted upon by an unbalanced force.

This is only a part of the 1st law. According to this breakdown, an object at rest (not moving) will stay at rest unless an external upon acts upon it. For example, if you see a ball on the ground, it will not move unless you or another force kicks it. The same is true for other objects. They will not change their position unless an external force is applied to that object.

Some other examples:

1. REM Sleep: REM Sleep (also known as dream sleep) is the sleep in which the body is paralysed so that it won’t do any harm to itself or others. In this state, the body is at rest.
2. Stopped Clock: When the batteries of a clock run out, the time stops.
3. Dress in the wardrobe: The dress kept in a hanger untouched is another example of the object at rest.
4. Golf ball: Unless acted upon by an unbalanced force, a golf ball would sit on the tee forever.

This is the concept of rest in Physics. Now let’s understand the concept of motion.

MOTION

It describes various components of a moving object. The variables that are derived from the kinematic motions are velocity, displacement, and time. Laws of constant acceleration included three equations. These can only be applied when the acceleration of constant motion is defined to a single line. The equations are as below:

1. v = u at
2. v2 = u2  2as
3. s = ut 1/2at2

Here:

• u stands for initial velocity
• v stands for final velocity
• a stands for acceleration
• t stands for time
• s stands for displacement

|An object is in motion when its distance from another object is changing

Earlier, we understood that an object is in motion when its velocity is more significant than zero. For an object to cover a certain distance from one position to another, it needs speed to make its way. Newton’s 1st law of motion says,

“An object at rest will stay at rest, and an object in motion will stay in motion at constant velocity unless acted upon by an unbalanced force.”

What is this unbalanced force that acts on an object in motion?

=> Friction – The sliding and rolling of one solid object over one another is known as Friction. Traction needed to walk without slipping may be beneficial, but they also present a great measure of opposition to the motion.

There are four main types of friction:

Sliding friction: Ice skating

Rolling friction: Bowling

Fluid friction(air or fluid): Air or water resistance

Static friction: Initial friction when moving an object

If you slide a book across a table, it will slide to a rest position. Try this!

The book comes to rest because of the presence of a force. This force is friction which brings the book to a halt. But what would happen if there was no friction?

According to Newton’s first law of motion, a moving object that is not acted on by an unbalanced force will

1. Eventually come to a stop
2. Remain in motion
3. Accelerate in the absence of friction
4. Transfer its energy to another object?

The correct answer is B. If there is no friction, then the object in motion will remain in motion.

TYPES OF MOTION

There are four basic types of motion:

1. Rotary Motion: The object rotates around rotation on a fixed axis. This is known as Rotary Motion. For instance, a figure skater rotating on an ice rink.
2. Oscillatory Motion: The object continuously repeats in the same motion like a swing.
3. Linear Motion: A one-dimensional motion on a straight line, like an athlete running on a straight track.
4. Reciprocating Motions: A repetitive and continuous up and down or back and forth motion like a needle in a sewing machine.

These are basic types of motion. There are other types of motion as per state of motion, directions, and others.

Let us look at six more types of motions, which are:

1. Oscillatory Motion
2. Rotational Motion
3. Translational Motion
4.  Periodic Motion
5. Circular Motion
6. Linear Motion
7. OSCILLATORY MOTION

It is the kind of motion that is repeated again and again after a certain interval. The oscillatory motion will never come to a halt if there is an absence of friction, but in the real world, it eventually stops. Some examples are,

• A swinging swing
• The motion of a pendulum
• A boat tossing up and down a river
• The tuning fork
1. ROTATIONAL MOTION

The motion of a body is so that all of its particles move in circles (rotate) about an axis. Rotational motion is illustrated by

• The fixed speed of rotation of the Earth about its axis
• The varying speed of rotation of the flywheel of a sewing machine
• The rotation of a satellite about a planet, in which both the speed of rotation and the distance from the centre of rotation may vary
1. TRANSLATIONAL MOTION

When all the parts of an object move the same distance in a given time is known as transitional motion. For example,

• A cycle moving on a track
• A man walking on the road
• Birds flying in the sky
1. PERIODIC MOTION

A motion that repeats itself after equal intervals of time is known as periodic motion. Commonly, the objects under this motion are mostly in the to and fro motion. For example,

• A moving pendulum
• Hands of a working clock
• The earth rotating on its axis
1. CIRCULAR MOTION

It is the movement along the border(circumference) of a circle about a fixed centre. For example,

• A bicycle or a car moving on a circular track of the park
• The motion of the moon around the earth
1. LINEAR MOTION

Linear motion can be defined as the movement of a body on a straight line without any deviation.  Example

• An athlete running on a straight track
• A bullet shot from a pistol always moves in a straight line

Conclusion:

By now, you will understand the complete Fundamentals of Rest and Motion in Physics by carefully going through the concepts of various types of motion, equations of motion, and formulas for equations of motion. You also understand rest, friction such as sliding friction, Rolling friction, Fluid friction (air or fluid) and Static friction. Evaluate the concepts regarding various types of motion with definitions and examples. This will help you memorise things in a better manner. You need to go through everything carefully.

We hope this chapter was able to fulfil your requirement and need to understand the motion of physics.

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