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Rest: An object is at rest if its position does not change over time in relation to its immediate surroundings.Examples: A wooden chair kept on the floor, a tree rooted to the ground, a transmission tower fixed to the ground.Motion: An object is in motion if its position changes over time with respect to its immediate surroundings.Examples: A walking camel, a flying bird, a football kicked across a grassy field.The Relative Nature of Rest and Motion: Rest and motion are relative terms. A body can be simultaneously at rest with respect to one observer/object and in motion with respect to another.Example 1 (Moving Train): A passenger sitting inside a moving train is at rest relative to the train’s seats and roof because there is no relative change in position. However, the passenger is in motion relative to trees and houses outside the train.Example 2 (Sitting on the Ground): A person sitting in the open is at rest in relation to the ground. However, because the Earth rotates on its axis and orbits the Sun, the person is in motion relative to the Sun and celestial stars.
Rectilinear (Linear) Motion: Translatory motion along a straight line path.Examples: A bullet fired from a gun, a car driving down a straight road, an athlete running on a straight racing track, a coin sliding undeflected on a carrom board.Curvilinear Motion: Translatory motion along a curved line path.Examples: A car taking a turn on a curved road, a javelin thrown by an athlete, a basketball thrown into a hoop.
Examples: A girl swinging a ball tied to a string in a circular path, children riding on a merry-go-round, runner on a circular running track.
Examples: A spinning top, a rotating ceiling fan, the hands of an analog clock, a potter’s wheel, the Earth spinning on its axis.
Examples: The motion of a clock pendulum, a playground swing, a mass suspended from a string, the piston of an engine.
Examples of Vibratory Motion: Plucking the strings of a sitar or guitar, playing a drum or tabla, the movement of vocal cords during speech, a car body vibrating when the engine is ignited.
Critical Fact: Every oscillatory motion is periodic, but not every periodic motion is oscillatory (e.g., the Earth’s revolution is periodic but not oscillatory).Examples: A wall clock pendulum completing one oscillation every 2 seconds, clock hands repeating their position (seconds hand every minute, minutes hand every 60 minutes, hours hand every 12 hours), the Earth rotating around its axis every 24 hours, the Earth revolving around the sun every 365¼ days.
Examples: The swinging of human arms or legs while walking, the wheels of a car moving on a busy road (brakes applied frequently), a rolling ball gradually slowing down and stopping.
Rolling Motion: A specific combination of rotatory and translatory motion.Example 1 (Bicycle): The wheels perform rotatory motion while the bicycle itself moves forward in translatory motion.Example 2 (Drill Machine): The drill bit rotates (rotatory motion) while moving forward into the wood (translatory motion).Example 3 (Well Pulley): The pulley wheel rotates (rotatory motion) while the rope and bucket move vertically (translatory motion).
Examples: A flying mosquito, a football or hockey player moving during a game, smoke particles drifting in air, a flying kite.
Definition: A system consisting of a small, heavy mass (called the bob) suspended by a weightless, inextensible, and perfectly flexible string from a rigid, stationary support.One Complete Oscillation: The entire to-and-fro cycle of the bob about its mean position. It is completed when the bob starts from mean position 
, moves to extreme position 
, swings to the opposite extreme position 
, and returns back to .Time Period (
): The time taken by the pendulum to complete exactly one oscillation.Formula:
SI Unit: Second (
).Core Principle: The time period of a simple pendulum of a given length remains constant at a given place, irrespective of the distance (amplitude) moved by the bob in each oscillation.
The actual path length covered by a moving object, independent of the direction of travel.SI Unit: Metre (
). Other units: Centimetre (
), Kilometre (
).Note: Since path length cannot be negative, distance is always positive.
The distance travelled by an object per unit of time.Formula:
SI Unit: Metre per second (
). Other units: Kilometre per hour (
) for fast vehicles, Centimetre per second (
) for slow objects like ants.Measurement Devices:Speedometer: Displays the real-time speed of a vehicle.Odometer: Records the cumulative distance travelled by the vehicle (in kilometres).
Uniform Motion: When an object covers equal distances in equal intervals of time (moving with a constant/uniform speed).Non-Uniform Motion: When an object covers unequal distances in equal intervals of time (moving with a variable/non-uniform speed).Examples: A train slowing down to stop at a station, a ball rolling and stopping, a car on a crowded street when brakes are applied.
Used to describe the overall rate of motion for objects moving with non-uniform speeds.Formula:
The distance travelled by light in one year.Value: 
. Used to measure vast astronomical distances.
Mass: The total quantity of matter contained within a physical body.Weight: The force of gravitational attraction exerted by the Earth (or another celestial body) pulling an object towards its centre.Variability of Weight:Poles vs. Equator: Weight is maximum at the poles (where gravitational force is strongest) and minimum at the equator (where gravitational force is weakest).Altitude: Weight decreases as altitude increases because gravitational pull diminishes with distance from Earth’s surface.Celestial Bodies: Weight depends on the mass of the planet. Because Earth has a larger mass than the Moon, its gravitational pull is greater. Thus, a person weighs less on the Moon than on Earth, despite having the exact same mass.Weightlessness: A sensation experienced when a body is not in contact with any other body and is acted upon strictly by gravity (e.g., freely falling bodies or astronauts in deep space without contact forces).Units of Weight:SI Unit: Newton (
). (The gravitational force acting on a mass of approximately 
or 
on Earth).Gravitational Units: Kilogram-force (
) and gram-force (
).Weight of a 
mass = 
(or 
approx).Weight of a 
mass = 
(or 
approx).
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Prepared by: learnloophq@gmail.com
Chapter: 02. Motion
MOTION: COMPREHENSIVE CRASH COURSE REVISION MATERIAL
1. REST AND MOTION
2. TYPES OF MOTION
Different objects move in distinct ways depending on their paths and structural movements:
A. Translatory Motion
The motion of an object in which every single point of the body moves through the exact same distance in the same interval of time.
B. Circular (Circulatory) Motion
The motion of an object around a fixed central point along the circumference of a circle.
C. Rotatory Motion
The motion of a body about a fixed axis. Different points of the body cover different distances in the same time interval; points closer to the axis travel smaller distances than points farther away.
D. Oscillatory Motion
The to-and-fro or back-and-forth movement of an object about its mean (resting) position. The maximum distance covered on either side of the mean position is equal.
E. Vibratory Motion
The motion of only the parts of a body about its mean position (instead of the entire body moving). This is driven by the oscillations of the constituent atoms.
Key Differences: Oscillatory vs. Vibratory Motion
Oscillatory Motion
Vibratory Motion
The whole body moves to and fro about its mean position.
Only parts of the body move; the whole body does not change its position.
There is no physical change in the shape of the body.
There is a physical change in the shape of the body during motion.
The distance traversed on either side of the mean position is always equal.
The distance traversed on either side of the mean position may not be equal.
This motion always occurs along a straight line.
This motion can take place in any direction.
F. Periodic Motion
Motion that repeats itself at fixed, regular intervals of time.
G. Non-Periodic Motion
Motion that does not repeat itself at fixed, regular intervals of time.
H. Complex (Multiple) Motion
Motion that is a combination of two or more distinct types of motion occurring simultaneously.
I. Random (Zig-Zag / Irregular) Motion
Motion in which an object changes its direction frequently and unpredictably.
3. THE SIMPLE PENDULUM
4. DISTANCE, SPEED, AND UNIFORMITY
Distance
Speed
Uniform vs. Non-Uniform Motion
Average Speed
Light Year
5. MASS AND WEIGHT
Though used interchangeably in everyday language, mass and weight are separate scientific concepts:
Key Differences: Mass vs. Weight
Mass
Weight
The amount of matter contained in a body.
The gravitational force with which the Earth attracts a body.
A constant quantity that does not change from place to place.
A variable quantity that changes depending on local gravity.
Can never be zero.
Can be zero if no gravitational force is acting on it.
SI unit is the Kilogram (
).
SI unit is the Newton (
).
Measured using a beam balance or physical balance.
Measured using a spring balance.
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