Motion in Physics: Definition, Types, Laws, and Examples

Motion: In Physics, Motion is defined by the change in position of a body over time. For example, going to school from home, picking a glass to drink water, moving a chair to seat on it, and so on. The motion of a body is always observed with respect to a frame of reference. Moreover, we measure the change in position of the body relative to that frame with a change in time.

All bodies or things in the universe perform the motion. However, when we compare it to a frame of reference that is moving together with the body, then we can’t define its motion and we say that the body is at rest. Students can read the article to know the definition, types, laws, and examples of motion.

Motion Definition

Motion is defined as the change in position of an object with respect to its surroundings in a given interval of time. It is one of the important topics of Classical Mechanics as well as Physics. When it comes to measuring a motion, we need to compare a body with a frame of reference and time.

For example, a girl is riding a cycle. She starts riding the cycle from her house and in 20 minutes she reaches the market. Thus, she moves from one place to another in 20 minutes. So, we can say that the girl is in motion during that time.

Types of Motion

There are various types of motions in Physics. Candidates can check the different types below:

Translational Motion
Rotational Motion
Linear Motion
Periodic Motion
Simple Harmonic Motion
Projectile Motion
Oscillatory Motion

Translational/Linear Motion

When an object moves uniformly in the same direction it is called the translational or linear motion. For example, a bus or a person moving along the road. There are two types of translational motion:

Rectilinear Motion: When a body moves along a straight line/path, it is called rectilinear motion. For example, the motion of a car along a straight path.
Curvilinear Motion: When a body moves along a curved line/path, it is known as curvilinear motion. For example, the movement of a snake.

Rotational/Circular Motion

When an object moves along a circular path around a fixed axis it is called the rotational or Circular motion. For example, the rotation of the earth along its axis or the rotation of a merry-go-round.

Periodic Motion

It is the motion of a body that repeats itself after a fixed interval of time. For example, the movement of a hand of a clock.

Projectile Motion

It is a type of motion in which an object has a horizontal displacement as well as vertical displacement. For example, throwing a ball and take-off and landing of a plane.

Oscillatory Motion

When an object moves to and fro about its mean position, it is known as oscillatory motion. For example, the movement of the bob of a simple pendulum and a swing.

Motion Related Terms

To find out the motion of an object, there are some commonly used terms. Basically, motion is mathematically described in terms of the following quantity:

Distance: The total path or length covered by an object moving from one point to another is called distance. It is a scalar quantity. Furthermore, its SI unit is meter (m).
Displacement: It is the shortest distance from the initial to the final position of an object undergoing motion. It is a vector quantity whose SI unit is also meter (m).
Time: It is a scalar quantity. Its SI unit is seconds (s).
Speed: It is defined as the total distance travelled or covered by an object in a unit of time. It is a scalar quantity. Moreover, its SI unit is meter per second (ms^–1).
Velocity: It is defined as the total displacement of an object with respect to a frame of reference in a unit of time. It is a vector quantity and its SI unit is also meter per second (ms^–1).
Acceleration: It is defined as the rate of change of the velocity of an object with respect to time. It is a vector quantity. Furthermore, its SI unit is meter per second square (ms⁻²).

Laws of Motion

Newton, a well-known Physicist, provided three laws of motion. Furthermore, these Newton’s laws of motion are the fundamentals of classical mechanics. With minor limitations, these laws are valid anywhere as well as everywhere. Students can check the three laws of motion below:

First Law

According to Newton’s first law of motion, an object remains at rest or in uniform motion until an external force is applied to it. The first law is also known as the law of inertia. When an object resists any change in its existing state of rest or motion, it is called inertia.

Second Law

The second law of motion states that the rate of change of momentum of an object is directly proportional to the applied force and is in the direction of the force. The second law can be expressed in the following equation:

F = ma

Where ‘F’ is the applied force, ‘m’ is the mass of the object, and ‘a’ is the acceleration of the object.

Third Law

The third law of motion states that every action has an equal and opposite reaction. For example, if an object exerts a force on the ground, then the ground will also exert an equal and opposite force on the object.

Equations of Motion

The following are the three equations of motions:

v = u + at
s = ut + (1/2)at²
v² – u² = 2as

Where ‘u’ is the initial velocity, ‘v’ is the final velocity, ‘s’ is the distance covered by an object, ‘t’ is the time taken, and ‘a’ is the acceleration of an object.

Candidates can get complete information on Motion from this article. Furthermore, please reach out to us using the comment box if you have any doubts or queries regarding the article. We will get back to you at the earliest.

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