Swipe across notes and practice
CBSE | Class 9 | science
Read the chapter in a clean notebook-style flow before moving into deeper practice.
Summary Note
Key concept recap
Motion is the change in position of an object with respect to time and a reference point.
Everything in the universe, from tiny atoms to large galaxies, exhibits motion.
Motion can be perceived directly or indirectly by observing effects such as displacement of leaves, movement of shadows, or changes in seasons.
Summary Note
Key concept recap
Motion can be of different types: translational (straight-line), circular, rotational, and vibrational.
Some objects may show complex motion combining more than one type.
In this chapter, motion along a straight line is primarily discussed, along with its graphical and mathematical descriptions.
Summary Note
Key concept recap
Distance is the total path length covered by an object; it is a scalar quantity with only magnitude.
Displacement is the shortest straight-line distance between the initial and final position; it is a vector with both magnitude and direction.
Displacement can be zero even when distance is not, such as when an object returns to its starting point.
Summary Note
Key concept recap
Uniform motion refers to motion in which an object covers equal distances in equal intervals of time.
Non-uniform motion refers to motion where unequal distances are covered in equal intervals.
Most motions in daily life, like walking or driving through traffic, are non-uniform.
Summary Note
Key concept recap
Speed is the distance travelled per unit time and is a scalar quantity. Its SI unit is m/s.
Velocity is the displacement per unit time and is a vector quantity.
Average speed is total distance divided by total time; average velocity is total displacement divided by total time.
Summary Note
Key concept recap
Acceleration is the rate of change of velocity with time. It has both magnitude and direction (vector).
Uniform acceleration refers to a constant rate of change in velocity, such as a freely falling body.
Non-uniform acceleration involves varying changes in velocity over time.
Summary Note
Key concept recap
Distance-time and velocity-time graphs are used to represent motion.
In a distance-time graph, uniform motion appears as a straight line, while non-uniform appears as a curve.
In a velocity-time graph, the area under the graph gives the distance travelled, and slopes represent acceleration.
Summary Note
Key concept recap
Three key equations describe motion under uniform acceleration:
1. v = u + at
2. s = ut + ½at²
3. v² = u² + 2as
These relate displacement (s), initial velocity (u), final velocity (v), acceleration (a), and time (t).
Summary Note
Key concept recap
An object moving with constant speed along a circular path is in uniform circular motion.
Though speed remains the same, the direction changes continuously, making it an accelerated motion.
Examples include motion of planets, satellites, and spinning objects like hammers or stones tied to a string.
Summary Note
Key concept recap
Distance – Total path length travelled, scalar quantity.
Displacement – Shortest distance between two positions, vector quantity.
Speed – Distance per unit time (scalar).
Velocity – Displacement per unit time (vector).
Acceleration – Rate of change of velocity.
Uniform Motion – Equal distances in equal time intervals.
Non-uniform Motion – Unequal distances in equal time intervals.
Equations of Motion – Set of formulas relating velocity, displacement, acceleration, and time.
Uniform Circular Motion – Motion with constant speed along a circular path.
