ANAND CLASSES study material and notes explore the key differences between one-dimensional, two-dimensional, and three-dimensional motion with detailed explanations, real-life examples for JEE, NEET, and CBSE Board Class 11 Physics.
Motion is the change in position of a body with respect to time. Motion can be classified into different types based on the number of dimensions in which the body moves.
One-Dimensional Motion
Motion of a body in a straight line is called one-dimensional motion.
In this type of motion, only one coordinate of the position of the body changes with time.
Example:
Motion of a car on a straight road.
Motion of a freely falling body.
Two-Dimensional Motion
Motion of a body in a plane is called two-dimensional motion.
Here, two coordinates of the position of the body change with time.
Example:
Motion of a car on a circular turn.
Motion of a billiards ball on the table.
Three-Dimensional Motion
Motion of a body in space is called three-dimensional motion.
All three coordinates of the position of the body change with time.
Example:
Motion of a flying kite.
Motion of a flying insect.
Difference Between One-Dimensional, Two-Dimensional, and Three-Dimensional Motion
Feature
One-Dimensional Motion (1D)
Two-Dimensional Motion (2D)
Three-Dimensional Motion (3D)
Definition
Motion along a single axis (straight line).
Motion in a plane (two perpendicular axes).
Motion in space (three perpendicular axes).
Axes Involved
Only one axis (X or Y or Z).
Two axes (X-Y or Y-Z or X-Z).
Three axes (X, Y, and Z).
Examples
– A car moving on a straight road. – A freely falling object under gravity. – A train moving along a straight track.
– Projectile motion (like a ball thrown at an angle). – Circular motion in a plane (like a satellite orbiting Earth). – A car taking a turn on a curved road.
– The motion of an airplane in air. – The movement of a fish in water. – The flight of a bird.
Equations of Motion
Kinematic equations apply in one dimension.
Vector form of kinematic equations used in two directions.
Kinematic equations extended to three directions.
Velocity & Acceleration
Only one component (e.g., vxv_xvx).
Two components (e.g., vx,vyv_x, v_yvx,vy).
Three components (e.g., vx,vy,vzv_x, v_y, v_zvx,vy,vz).
Graphical Representation
Represented as a straight-line graph in displacement-time graph.
Motion is represented as a curve in a plane.
Motion is represented as a trajectory in space.
Key Takeaways:
1D Motion: Movement in a straight line (e.g., free fall, straight road).
2D Motion: Movement in a plane (e.g., projectile motion, circular motion).
3D Motion: Movement in space (e.g., flight of a drone, motion of planets).
Conclusion
1D Motion: Uses simple kinematic equations in a straight line.
2D Motion: Involves components of motion (projectile, circular motion).
3D Motion: Involves three velocity components, requiring vector calculations.
FAQs
Q1: What is motion?
Motion is the change in position of a body with respect to time.
Q2: What is one-dimensional motion?
Motion that occurs along a straight line where only one coordinate changes with time.
Q3: Give two examples of two-dimensional motion.
Motion of a car on a circular turn, motion of a billiards ball.
Q4: What is the difference between 2D and 3D motion?
In two-dimensional motion, only two coordinates change, while in three-dimensional motion, all three coordinates change.
MCQs with Answers and Explanation
Q1: Which of the following is an example of one-dimensional motion?
A) Motion of a car on a straight road B) Motion of a car on a circular path C) Motion of a flying bird D) Motion of a billiards ball
Answer: A) Motion of a car on a straight road. Explanation: In one-dimensional motion, the body moves in a straight line, meaning only one coordinate changes.
Q2: Which type of motion does a freely falling object exhibit?
A) One-dimensional motion B) Two-dimensional motion C) Three-dimensional motion D) Rotational motion
Answer: A) One-dimensional motion Explanation: A freely falling object moves along a straight vertical path, changing only its height (one coordinate).
Conceptual Questions with Answers
Q1: Can a body have two-dimensional motion with only one coordinate changing?
No, for two-dimensional motion, two coordinates must change with time.
Q2: A projectile is fired from the ground at an angle. What type of motion does it exhibit?
It exhibits two-dimensional motion because it moves in both horizontal and vertical directions.
Do You Know?
A satellite orbiting Earth follows two-dimensional motion if viewed in a particular plane but three-dimensional motion if considered in space.
The motion of air molecules is an example of random three-dimensional motion.
The movement of a river is typically one-dimensional motion if it flows in a straight line.
Worksheet
Define motion.
Differentiate between 1D, 2D, and 3D motion.
Provide two examples of each type of motion.
Identify the type of motion for the following cases: a) A bird flying in the sky b) A car moving on a curved road c) A ball dropped from a height
Explain why a projectile follows a two-dimensional path.
Test Paper (Total: 10 Marks)
Define motion. (2 Marks)
What are the conditions for motion to be classified as one-dimensional? (2 Marks)
Give one example each of 1D, 2D, and 3D motion and justify your choice. (3 Marks)
A ball is thrown at an angle. What type of motion does it exhibit? Explain. (3 Marks)
Important Points for Quick Revision
Motion is classified based on dimensions: 1D, 2D, and 3D.
One-dimensional motion occurs in a straight line (e.g., a falling ball).
Two-dimensional motion occurs in a plane (e.g., projectile motion).
Three-dimensional motion occurs in space (e.g., motion of an insect).
A freely falling body moves in one dimension, while a projectile moves in two.
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