Motion is the change in position of an object with respect to time and a reference point.

What is rest in physics?

An object is said to be at rest if it does not change its position with respect to its surroundings.

Distance is the total path length covered by an object during motion.

Displacement is the shortest straight-line distance between the initial and final positions of an object.

What is the SI unit of distance and displacement?

The SI unit for both distance and displacement is metre (m).

Speed is the distance covered by an object per unit time.

What is average speed?

Average speed is the total distance traveled divided by total time taken.

Velocity is the rate of change of displacement with respect to time.

What is the SI unit of speed and velocity?

The SI unit for both is metre per second (m/s).

What is uniform motion?

Motion in which an object travels equal distances in equal intervals of time is uniform motion.

What is non-uniform motion?

Motion in which an object covers unequal distances in equal intervals of time is non-uniform motion.

What is acceleration?

Acceleration is the rate of change of velocity with respect to time.

Give the formula for acceleration.

a = (v - u) / t, where v is final velocity, u is initial velocity, and t is time.

What are the SI units of acceleration?

Metre per second squared (m/s²).

NCERT Class 9 Science Chapter 7 Motion Notes, MCQs & Solutions

12 CBSE Marks

★★★★★ Difficulty

10 Topics

Very High Board Weight

Topics Covered

10 key topics in this chapter

Rest & Motion

Distance vs Displacement

Uniform & Non-uniform Motion

Speed & Velocity

Acceleration

Distance–Time Graph

Velocity–Time Graph

Equations of Motion

Graphical Derivation of Equations

Uniform Circular Motion

Study Resources

📖 NCERT Notes ✏️ MCQ Practice ✅ True / False Quiz 📝 Exercise Solutions

Key Concepts

01. Distance vs Displacement

Distance is the total path length — scalar, always positive. Displacement is the shortest straight-line distance from start to end — vector, can be zero or negative. They are equal only for straight-line motion in one direction.

02. Speed vs Velocity

Speed = distance / time (scalar). Velocity = displacement / time (vector). Average speed = total distance / total time. Average velocity = total displacement / total time. They are equal only for straight-line, one-direction motion.

03. Acceleration

Acceleration = change in velocity / time = (v − u) / t. Positive acceleration: speeding up. Negative acceleration (retardation/deceleration): slowing down. Uniform acceleration: constant rate of change of velocity.

04. Distance–Time & Velocity–Time Graphs

D-T graph: slope = speed. Straight line = uniform speed. Curve = non-uniform speed. V-T graph: slope = acceleration. Area under V-T graph = displacement. Straight line = uniform acceleration.

05. Equations of Motion

For uniform acceleration from initial velocity u, final velocity v, time t, displacement s, acceleration a: (1) v = u + at, (2) s = ut + ½at², (3) v² = u² + 2as. Memorise all three.

06. Uniform Circular Motion

A body moving in a circle at constant speed has changing velocity (direction changes) — so it is accelerated. This centripetal acceleration is directed towards the centre. Period T = circumference / speed = 2πr / v.

Formulas at a Glance

#	Name	Expression	Notes
01	Speed	`v = d/t`	Distance ÷ time
02	Acceleration	`a = (v − u)/t`	Change in velocity ÷ time
03	1st Equation	`v = u + at`	Velocity–time relation
04	2nd Equation	`s = ut + ½at²`	Displacement–time relation
05	3rd Equation	`v² = u² + 2as`	Velocity–displacement relation
06	Circular Period	`T = 2πr/v`	Time for one complete revolution

Important Notes

An odometer measures distance; a speedometer measures speed — not velocity.

A body can have zero displacement with non-zero distance (e.g., complete circular trip). A body can have zero acceleration with non-zero velocity (uniform motion).

Area under a V-T graph gives displacement, not distance — for negative velocity segments, subtract that area.

All three equations of motion assume uniform (constant) acceleration. They do NOT apply to non-uniform acceleration.

Exam Tips & Common Mistakes

In every numerical, write the given data (u, v, a, t, s), identify the unknown, select the appropriate equation of motion.

V-T graph questions: slope = acceleration (including units m/s²). Area = displacement (units m). Both tested every year.

Uniform circular motion — speed is constant but velocity is NOT constant (direction changes). This is a common trick question.

"A car starts from rest" → u = 0. "Comes to rest" → v = 0. "Uniform speed" → a = 0. Map these before solving.

Learn to derive the 3rd equation (v² = u² + 2as) graphically from V-T graph — it appears as a 3-mark derivation.

All Class IX Science Chapters

Ch 01 Ch 02 Ch 03 Ch 04 Ch 05 Ch 06 Ch 07 Ch 08 Ch 09 Ch 10 Ch 11 Ch 12

Motion