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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