Kinematics Terminologies

Kinematics

In kinematics, we study ways to describe motion without going into the causes of motion.

Important Terms

1. Rest - A body is said to be at rest if it does not change its position with respect to its surroundings with the passage of time.

e.g.: A book lying on the table.

2. Motion- Motion is known as a change in the position of an object with time.

e.g.: A moving bus.

• Note - Rest and motion are relative to each other.

e.g. All passengers sitting inside the moving bus are at rest with respect to one another. But all appears to be in motion to a man standing outside the bus.

Types of Motion

There are three types of motion.

I. One-Dimensional (1-D)-

• If only one coordinate is used to describe the motion of an object.

• Motion is a straight line in 1-D.

• E.g: Train running on singletrack, Apple falling from a tree

II. Two Dimensional (2-D)-

• When two coordinates are used to describe the motion of an object.

• Motion in-plane is 2-D.

• E.g. Earth revolves around the sun.

III. Three Dimensional -

• When all three coordinates are used to describe the motion of an object.

• Motion in space is 3-D.

• e.g.: an object moving in space.

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Now, let's move to the solved example for a better understanding of the kinematics terminologies concepts.

Solved Examples Based on Kinematics Terminologies

Example 1: A Geostationary satellite looks stationary from the Earth. Which of the following options is correct?

1) It is stationary

2) (correct) It is moving with velocity same as that of earth

3) Its velocity is greater than Earth’s velocity

4) Its velocity is less than Earth’s velocity

Solution:

Rest and motion are relative to each other. So a geostatistic satellite looks stationary from Earth means its position is fixed with respect to Earth as both are moving at the same speed.

Hence, the answer is the option (2).

Example 2: An insect is moving on a spherical surface from one point to another point with constant speed which will describe its motion in the best way?

1) 1-D motion

2) 2-D motion

3) (correct)

3-D motion

4) None of the above

Solution:

In Three Dimension (3-D) motion all three coordinates are used to describe the motion of an object.

Any point on a spherical surface can be best described by its three coordinates . Hence it represents 3-D motion.

Example 3: When a particle is in 3-dimensional motion, which among the following will change?

1) X – coordinate only

2) X and Y coordinate only
3) Y and Z coordinate only

4) X, Y and Z coordinates

Solution :

In three-dimensional (3-D) motion all three coordinates are used to describe the motion of an object.

So In 3 -dimensional motion, all three coordinates will change.

Hence, the answer is the option (4).

Example 4: A stone falling vertically downwards is an example of -

1) 1-D motion

2) 2-D motion

3) 3-D motion

4) None of the above

Solution:

There are three types of motion.

1)One–Dimension

2)Two-Dimension

3)Three- Dimension

In 1- D motion, only one coordinate is used to describe the motion of an object.

As Stone is moving in a straight line and motion in a straight line can be described by a single coordinate. So it is a 1-D motion.

Hence, the answer is the option (1).

Example 5: Pawan travelled from Delhi to Banglore by aeroplane. This motion is an example of

1) 1-D motion

2) 2-D motion

3) 3-D motion

4) None of the above

Solution:

Three Dimensions (3-D). -

When all three coordinates are used to describe the motion of an object.

$\rightarrow$ Motion in space is 3-D.
wherein

e.g.: an object moving in space.

Hence, the answer is the option (3).

Conclusion

In this article on kinematics terminology, we've covered the basics of kinematics, which involves studying motion without considering its causes. We discussed key terms, and types of motion, and provided practical examples. Understanding these concepts is crucial for the mechanics section and more advanced topics in physics and is fundamental for various applications in science and technology.