What is Motion in Physics? Types and Laws of Motion

Motion, you have generally seen many things moving in your daily life. The movement of different vehicles, flying birds in the sky, crawling of animals on the land, swimming of fish or swimmers in the water, and so many other items.

All of them move in different manners. Some proceed in a straight line, some in a circular way. Not everyone moves in the same manner. So what are the different laws of motion, can you think of them?

This article will let you learn about the laws of motion and all the different types of laws of motion.

What is Motion in Physics?

Motion means the change of location in space-time. In Newtonian or classical physics, motion means changing position over time. It can be uniform or non-uniform. A rolling toy falls off a table, water flowing from the tap, rattling windows etc., all exhibit motion.

Even the air that you breathe exhibits motion! Everything in the universe moves. You live in a universe that is in continual motion. The fundamental particle of a matter, i.e., an atom, is in constant motion too. The motion can either be swift or slow, but motion exists.

In simple language, you can say that motion is a fact to leave an absolute place and go to another absolute place.

Definition of Motion

In actuality, there is no particular definition of motion. It is the movement of an article from one place to another, or you can hypothesise it is an activity of moving or changing place or position. The motion requires force to cause that change.

It is an important aspect of Physics. In short, it is the change in position of an object concerning a reference point. In the absence of a reference point, it means you will not be able to state whether an object is at a stationary position or in motion.

Types of Motion

There are six types of motion. They are further divided into subcategories.

1. Translatory Motion:

It is the motion in which all ends of a moving body move systematically in the same direction or line. If an object executes translational motion, then its orientation is no change relative to a fixed point. 

Translational motion is further classified into two categories:

• Rectilinear motion: When a body moves in a straight line. For instance, moving a cart in a straight line from point A to B.
• Curvilinear motion: When a body moves on a curve path. For instance, projectile motion.

Some examples of translational motion are:

• The motion of the train.
• Cat walking.
• The motion of the Earth.
• Moving of a coin over carrom board.
• The motion of birds.
• Sailing a boat in the sea.
• The motion of insects.
• Man walking.
• The motion of an aeroplane.
• A stone falls straight toward the Earth’s surface.
• The motion of gas molecules.

2. Linear Motion:

The switch in position from one place to another in a straight line in one dimension is known as linear motion. It means the change of position of an object to the time interval.

Linear motion is further classified into two categories:

• Uniform motion: When an object moves in a straight line with a constant speed. For instance, driving a car on the highway with a speed of 30 km/h.
• Non-uniform motion: When an object covers unequal distances in an unequal time interval. For instance, moving a car in a crowded area.

Some examples of linear motion are

• The movement of the vehicles on the road.
• Elevator movement in a building.
• The kicking of the football on the ground.
• Free-fall of objects from a certain height.
• The sliding of a boy in a straight line.
• Dragging a box from a path.
• The movement of an asteroid.

3. Circular Motion:

If a body follows a circular path, the motion is known as circular motion. Uniform circular motion is a particular type of circular motion in which the motion of a body following a circular path is at a constant speed. The object has a fixed central point and remains at an equal distance from it at any given position.

Circular motion is further classified into two categories:

• Uniform circular motion
• Non-uniform circular motion

Some examples of circular motion are:

• The electron’s motion around the nucleus.
• The movement of a merry-go-round.
• The motion of a toy car on the circular track.
• Running on a circular track.
• Planets around the Sun.
• The movement of a stone that is tied to a string.

4. Rotatory Motion

If a body advances about a certain axis without disturbing the radius of its motion, then the motion is known as rotatory motion.

Rotatory motion is further classified into two categories:

• Spin motion
• Orbit motion

Some examples of rotatory motion are:

• The Earth’s motion about its topographical axis that causes night and day is rotatory.
• Rotating a skater on an ice rink.
• The movement of the car’s wheel about its axis.
• The rotation of a fan.
• The movement of a spinning wheel.

5. Oscillatory Motion

When any object moves over a point repetitively, this type of motion is the Oscillatory Motion.

Oscillatory motion is further classified into two categories:

• Linear oscillatory motion: When an object moves left and right or up and down. For instance, the movement of the fluid in a U-tube column.
• Circular oscillatory motion: When an object moves left to the right but in circular form. For instance, the motion of a wheel.

Some examples of circular motion are:

• The vibration of strings of the musical instruments.
• The movement of a pendulum in the wall clock.
• Floating of ships or big vessels in the sea.
• A stringed object suspended on a nail.
• Motion of swing
• The motion of the solid sphere in a half hollow sphere.

6. Periodic Motion

If a body returns its motion along a fixed path, about a definite point after a certain time interval is known as periodic motion. The firm interval of time after which the motion is repeated is called the period of motion.

Some examples of periodic motion are:

• The progress of the hands of a clock.
• A simple pendulum.
• A rocking chair.
• The movement of the Earth in its orbit around the Sun.
• A wave in water.

Laws of Motion

In 1686, Sir Isaac Newton formulated three laws of motion. These laws give a scientific relationship between the forces that act on a body and the changes that occur due to this force.

The three laws of motion are:

1. First Law of Motion by Newton:

This law affirms that if a body is in motion, it remains in motion, while if the body is in rest, it remains in rest unless an external force applies. This law is also known as the law of Galileo or the law of inertia.

2. Second Law of Motion by Newton:

This law states that the change rate of a body’s momentum is directly comparable to the claimed force on the body and takes place in the direction of the force. This law gives the magnitude of force.

Force = mass x acceleration

F = ma

3. Third Law of Motion by Newton:

This law states that every action has equal and opposite reactions. Also, the action and reaction occur in two different bodies.

For example, a gun’s recoil, rocket’s motion, swimming, etc.

Conclusion

Now, to answer what is motion, you can say that a motion is something being someplace else than a moment before. In physics, the definition of motion is the change of position of an object relative to a fixed point. Mathematically, it is described in several ways: distance, displacement, speed, velocity, acceleration, and time.

Every physical process in the universe is composed of motion of some sort. It would be superb if you give due attention to the study of motion because of its importance in the physical world.

Frequently Asked Questions 

Q1. What is free-fall motion?

Answer: In Newtonian physics, free fall is any body motion where gravity is the only force working upon it. In the context of general reliance, where gravitation is decreased to a space-time curve, a body in free fall has no force reserved on it and moves along a geodesic.

Q2. Give examples of the body in motion, but it cannot be seen directly.

Answer: Some examples where motion is occurring, but you cannot check it with naked eyes are

• The flow of electrons in an electric wire that is carrying electrical current.
• Spin angular momentum of a spin 1/2 particle such as an electron, proton or neutron.
• The shifting of an electron from one energy level to a lower energy level in spontaneous emission of light.
• Orbital angular momentum of an electron in an atom orbiting the nucleus.

Q3. What are one-dimension, two-dimension, and three-dimension motion?

Answer: Motion in Physics is described as the changes in the object’s position concerning time. Based on a Cartesian coordinate system, motion is of three types:

• One-dimensional motion: The motion of a particle in a straight line can be described by only one component, either by its velocity or acceleration. For instance, the motion of a block in a straight line is one-dimensional.
• Two-dimensional motion: This type of motion takes place in a 2-D plane, and its velocity and acceleration are described in two mutually perpendicular directions. For instance, the motion of a stone thrown vertically upward with some angle. The projectile motion and circular motion are also termed 2-D motion.
• Three-dimensional motion: In this type of motion, three mutually perpendicular directions are required to specify its state, i.e., velocity, acceleration, and time. For instance, the motion of a bird or monkey in a 3-D space.