1. Motion
Motion is the change in position of an object with time with respect to a reference point.
Example: A moving car is in motion with respect to a person standing on the road.
2. Rest
Rest is the state of an object when its position does not change with time with respect to a reference point.
Example: A book lying on a table is at rest with respect to the table.
3. Reference Point
A reference point is a fixed point used to describe the position or motion of an object.
Example: If a shop is 250 m from home, then home can be taken as the reference point.
4. Position
Position is the location of an object with respect to a reference point. It is described using both distance and direction.
Example: A student is 10 m to the right of the classroom door.
5. Linear Motion
Linear motion is motion along a straight line. It is also called motion in a straight line.
Example: A train moving on a straight track.
6. Distance
Distance is the total length of the path travelled by an object.
It is a scalar quantity.
SI unit: metre (m)
7. Displacement
Displacement is the net change in the position of an object between two instants of time.
It is the shortest distance between the initial and final positions along with direction.
It is a vector quantity.
SI unit: metre (m)
8. Scalar Quantity
A scalar quantity is a physical quantity that has only magnitude and no direction.
Examples: Distance, speed, time, mass
9. Vector Quantity
A vector quantity is a physical quantity that has both magnitude and direction.
Examples: Displacement, velocity, acceleration
10. Magnitude
Magnitude means the numerical value of a physical quantity with its unit.
Example: In 20 m east, the magnitude is 20 m.
11. Time Interval
A time interval is the duration between two instants of time.
Example: From 2 s to 8 s, the time interval is 6 s.
12. Instant of Time
An instant of time is a single reading of a clock at a particular moment.
Example: 5 seconds is an instant of time.
13. Speed
Speed is the distance travelled by an object per unit time.
Formula:
Speed = Distance / Time
SI unit: m s⁻¹
14. Average Speed
Average speed is the total distance travelled divided by the total time taken.
Formula:
Average speed = Total distance travelled / Total time taken
15. Uniform Motion
Uniform motion is motion in which an object covers equal distances in equal intervals of time.
Example: A car covering 20 m every second.
16. Non-uniform Motion
Non-uniform motion is motion in which an object covers unequal distances in equal intervals of time.
Example: A car speeding up or slowing down.
17. Velocity
Velocity is the displacement of an object per unit time.
It tells both how fast the object is moving and in which direction.
Formula:
Velocity = Displacement / Time
SI unit: m s⁻¹
18. Average Velocity
Average velocity is the displacement divided by the total time interval.
Formula:
Average velocity = Displacement / Time interval
19. Acceleration
Acceleration is the rate of change of velocity with time.
Formula:
Acceleration = Change in velocity / Time interval
SI unit: m s⁻²
20. Average Acceleration
Average acceleration is the change in velocity divided by the time interval during which the change occurs.
Formula:
a = (v − u) / t
Here,
u = initial velocity
v = final velocity
t = time interval
21. Positive Acceleration
Positive acceleration occurs when the velocity of an object increases with time.
Example: A car speeding up.
22. Negative Acceleration
Negative acceleration occurs when acceleration is opposite to the direction of velocity. It usually happens when an object slows down.
It is also called retardation or deceleration.
Example: A car slowing down after brakes are applied.
23. Acceleration Due to Gravity
Acceleration due to gravity is the acceleration produced in an object due to Earth’s gravitational force.
It is denoted by g.
Near Earth’s surface:
g = 9.8 m s⁻²
24. Graph
A graph is a visual representation showing the relation between two quantities.
In motion, graphs are used to show how position or velocity changes with time.
25. Origin
The origin is the point where the x-axis and y-axis meet on a graph.
It is usually represented by O.
26. X-axis
The x-axis is the horizontal line on a graph.
In motion graphs, time is usually taken on the x-axis.
27. Y-axis
The y-axis is the vertical line on a graph.
In motion graphs, position or velocity is usually taken on the y-axis.
28. Position-Time Graph
A position-time graph shows how the position of an object changes with time.
In this graph:
Time is taken on the x-axis.
Position is taken on the y-axis.
29. Slope of Position-Time Graph
The slope of a position-time graph gives the velocity of the object.
A steeper slope means greater velocity.
30. Velocity-Time Graph
A velocity-time graph shows how the velocity of an object changes with time.
In this graph:
Time is taken on the x-axis.
Velocity is taken on the y-axis.
31. Slope of Velocity-Time Graph
The slope of a velocity-time graph gives acceleration.
Positive slope shows positive acceleration.
Negative slope shows negative acceleration.
Zero slope shows zero acceleration.
32. Area Under Velocity-Time Graph
The area under a velocity-time graph gives the displacement of the object.
For constant velocity:
Displacement = Velocity × Time
33. Kinematic Equations
Kinematic equations are equations used to describe motion in a straight line with constant acceleration.
The three main equations are:
v = u + at
s = ut + ½at²
v² = u² + 2as
34. Initial Velocity
Initial velocity is the velocity of an object at the beginning of a time interval.
It is usually represented by u.
35. Final Velocity
Final velocity is the velocity of an object at the end of a time interval.
It is usually represented by v.
36. Displacement Symbol
Displacement is usually represented by s in kinematic equations.
37. Motion in a Plane
Motion in a plane is motion in two dimensions.
Example: A kicked football moving through air.
38. Circular Motion
Circular motion is the motion of an object along a circular path.
Example: The motion of the tip of a clock hand.
39. Uniform Circular Motion
Uniform circular motion is motion in which an object moves in a circular path with constant speed.
Even though speed is constant, velocity changes because direction changes continuously.
40. Revolution
A revolution is one complete round of an object along a circular path.
Example: One complete round of a merry-go-round.
41. Circumference
Circumference is the total length of the boundary of a circle.
For a circle of radius R:
Circumference = 2πR
42. Tangent
A tangent is a straight line that touches a circle at only one point.
In uniform circular motion, the velocity at any point is along the tangent to the circular path.
Quick Revision Table
| Keyword | Meaning |
|---|---|
| Motion | Change in position with time |
| Rest | No change in position with time |
| Reference point | Fixed point used to describe position |
| Distance | Total path covered |
| Displacement | Net change in position with direction |
| Speed | Distance per unit time |
| Velocity | Displacement per unit time |
| Acceleration | Rate of change of velocity |
| Position-time graph | Graph of position against time |
| Velocity-time graph | Graph of velocity against time |
| Slope of position-time graph | Velocity |
| Slope of velocity-time graph | Acceleration |
| Area under velocity-time graph | Displacement |
| Uniform circular motion | Circular motion with constant speed |