INTERMEDIATE PHYSICS – LESSON 3

MOTION IN A PLANE

1. Introduction

Motion in a plane is a type of motion in which a particle moves in two dimensions simultaneously. Unlike motion in a straight line, here both x and y directions are involved.

Examples:

Motion of a ball thrown into air
Motion of a bird flying
Motion of a stone projected at an angle

2. Scalars and Vectors

(a) Scalar Quantities

Scalars have only magnitude and no direction.

Examples: distance, speed, mass, time

(b) Vector Quantities

Vectors have both magnitude and direction.

Examples: displacement, velocity, acceleration, force

3. Position and Displacement Vectors

The position of a particle in a plane is represented by a position vector drawn from origin to the point.

Displacement vector is the change in position vector.

Important: Displacement depends only on initial and final positions, not on the path.

📐 Insert Diagram: Position vector and displacement vector in XY-plane

4. Velocity and Acceleration in a Plane

In two-dimensional motion, velocity has two components:

Horizontal component (v_x)
Vertical component (v_y)

Resultant velocity is obtained by vector addition.

Key Formula:
v = √(v_x² + v_y²)

📐 Insert Diagram: Horizontal and vertical components of velocity

5. Projectile Motion

Projectile motion is the motion of a body thrown into air and moving under the influence of gravity alone.

Examples:

A ball thrown at an angle
A bullet fired from a gun

Assumptions:

Air resistance is neglected
Acceleration due to gravity is constant and acts downward

📐 Insert Diagram: Projectile motion showing parabolic path

6. Horizontal Projection

When a body is projected horizontally from a height, it follows a curved (parabolic) path.

Horizontal motion is uniform, while vertical motion is uniformly accelerated.

Important Concept:
Horizontal and vertical motions are independent of each other.

7. Relative Velocity (Basic Idea)

Relative velocity is the velocity of one object with respect to another.

Example: If two trains move in the same direction, relative velocity is the difference of their velocities.

8. Important Formulae (Intermediate Level)

Resultant velocity = √(v_x² + v_y²)
Horizontal displacement = v_x t
Vertical displacement = v_y t − ½gt²

9. Board Exam Focus Points

Difference between scalar and vector (2M / 4M)
Projectile motion explanation (8M)
Diagram-based questions are common
Formula-based numericals are scoring

➡️ NEXT: STAGE–2 – INTERMEDIATE EXAM QUESTIONS & NUMERICALS

Intermediate Physics Complete Notes – IIT JEE & Board Exams

This page contains complete Intermediate Physics notes along with IIT JEE materials, previous year questions, solved problems, diagrams, and exam strategies.

MIND GROW Magazine