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GRAVITATION in 1 Shot || FULL Chapter Coverage (Concepts+PYQs) || Class 9th Physics

Physics Wallah Foundation・128 minutes read

Gravity is integral to daily life, Newton's Apple Incident led to the discovery of gravity and Newton's Law of Gravitation describes its impact. From calculating gravitational force to understanding buoyant force, various physics concepts are explored, urging to move quickly through questions to grasp key concepts.

Insights

Sir Isaac Newton's contemplation on the falling apple led to the birth of the concept of gravity, which states that any two objects with mass will attract each other.
The formula for gravitational force is F = G * (m1 * m2) / d^2, with the value of the universal gravitational constant being 6.67 * 10^-11 Newton meter squared per kilogram squared.
Acceleration due to gravity is represented by g and is calculated using the formula G * m / r^2, with the value on Earth's surface being 9.8 m/s^2.
Archimedes' Principle explains why objects float or sink in water based on the balance of weight and upthrust forces, with water exerting an upward force on a body immersed in it.

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Recent questions

What is Newton's Law of Gravitation?
It states objects with mass attract each other.

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Summary

00:00

"Newton's Law of Gravitation and G"

Gravity plays a crucial role in our daily activities, as exemplified by Sir Isaac Newton's apple incident.
Sir Isaac Newton's contemplation on the falling apple led to the birth of the concept of gravity.
Newton's Law of Gravitation states that any two objects with mass will attract each other.
The formula for gravitational force is F = G * (m1 * m2) / d^2, where G is the universal gravitational constant.
The value of the universal gravitational constant is 6.67 * 10^-11 Newton meter squared per kilogram squared.
To derive the formula for G, cross multiply the force and distance, then divide by the product of the masses.
The SI unit for measuring force is the Newton, while distance is measured in meters and mass in kilograms.
The unit for the universal gravitational constant is Newton meter squared per kilogram squared.
Understanding the formula for G involves dividing the product of force and distance by the product of the masses.
The derived unit for G is crucial for calculating gravitational force accurately.

16:59

"Gravitational Constants: Essential Education for Children"

The gravitational constant is 6.67 * 10^-11 Newton Meters KG.
Children are encouraged to answer questions in the comment box to remember the value.
The formula for gravitational force is F = G * m * m / d^2.
Questions on Newton's Law of Gravitation are essential for understanding.
Understanding through questions is crucial for complete education.
The SI unit for the Universal Gravitational Constant is KG^2 / Newton meters^2.
Halving the distance between two bodies quadruples the gravitational force.
Gravitational force is integral to various phenomena like tides and planetary orbits.
Acceleration due to gravity is represented by g and is calculated using the formula G * m / r^2.
The value of acceleration due to gravity on Earth's surface is calculated as 9.8 m/s^2.

34:07

Newton, Gravity, and Earth's Forces

Newton is the unit of force
Newton is calculated as m*a, which is in kg per second square
The value of small g on Earth's surface is 9.81 meters per second square
The equatorial radius of Earth is greater than the polar radius
The value of g at the equator is lower than at the pole
The value of g changes with altitude and depth
The value of g decreases as an object moves above the surface or below Earth's surface
The value of g decreases as altitude increases, reaching zero in space
The value of g decreases with depth, becoming zero at the center of Earth
Universal Gravitational Constant (G) is 6.67 * 10^-11 newton meter square per kilogram

49:37

Understanding Weight, Mass, and Gravity in Physics

Earth attracts objects towards itself with a force called weight, which is the gravitational force.
Mass is constant, not variable, and remains the same regardless of location.
Bholu Uncle Ji's mass is 100 kg, and his weight varies depending on the location due to gravitational forces.
Weight changes depending on the location, showing that weight is not constant.
The formula to find weight is mass multiplied by gravitational acceleration (m * g).
The SI unit for weight is Newton, and for mass, it is kg or gram.
Free fall occurs when an object moves under the influence of gravitational force alone.
Free fall is when an object falls due to gravitational force without air resistance.
Equations of motion can be applied to objects in free fall with modifications.
The acceleration due to gravity (small g) is the constant force acting on objects in free fall.

01:06:16

"Revolutionizing Astronomy: Copernicus to Kepler"

Modify equations by replacing 'a' with 'g' and 's' with 'h'.
Understand the importance of using one's brain to solve problems.
Assign positive values to motion going upwards from a starting point and negative values to motion going downwards.
Always consider g as negative for downward motion.
Differentiate between positive and negative values based on the direction of motion from the starting point.
Discuss the historical shift from the geocentric theory to the heliocentric theory.
Nicolaus Copernicus challenged the geocentric theory and introduced the heliocentric theory.
Kepler's first law states that planets move in elliptical paths around the sun.
Kepler's second law emphasizes that a planet's aerial velocity around the sun remains constant.
Kepler's third law highlights the relationship between a planet's orbital period and its distance from the sun.

01:21:40

Planets' Orbits and Pressure in Fluids

The orbit of a planet near the Sun is small, while a planet farther away has a larger orbit.
The distance of a planet from the Sun affects the size of its orbit, with further planets having larger orbits.
The time taken for a planet to complete one revolution around the Sun is known as the time period of revolution.
Kepler's third law states that the period of revolution around the Sun is directly proportional to the cube of the mean distance of the planet from the Sun.
The relationship between the distance of a planet from the Sun and its time period of revolution is given by a constant, allowing for the determination of a planet's time period.
Thrust is a perpendicular force applied to a body, with thrust acting at 90 degrees to the body's surface.
Pressure is the thrust applied per unit surface area, with pressure being inversely proportional to the area.
Fluids, including liquids and gases, can flow and exert pressure on the walls and base of a container they are placed in.
The pressure exerted by a liquid is due to its weight, which is a gravitational force acting downwards.
The pressure caused by a liquid is a result of the weight of the liquid, which exerts a force in the downward direction.

01:37:46

"Pressure and Depth in Liquids Explained"

Holes made at the same height in a container result in water coming out at the same pressure.
Pressure in a liquid depends on density, acceleration due to gravity, and height from the free surface.
Pressure remains the same at a given depth in a liquid due to these factors.
Submarines have limited depths they can reach due to increasing pressure as they go deeper.
A submarine explosion was caused by increasing pressure as it went deeper into the ocean.
Making holes at different heights in a container results in different pressures and water flow rates.
Pressure at the base of containers is the same if they have the same height, regardless of shape or size.
Objects sink or float in water based on the balance of weight and upthrust forces.
Law of Flotation explains why objects float or sink in water based on weight and upthrust forces.
Archimedes' Principle states that objects in a fluid experience an upward force called upthrust.

01:52:23

Buoyant force, Archimedes' principle, and gravity.

Water exerts an upward force on a body when partially or completely immersed in it.
This force is known as buoyant force or upthrust, explained by Archimedes' principle.
Archimedes' principle states that the upward force on a body in a liquid is equal to the weight of the liquid displaced by the body.
When a body is submerged in a liquid, the volume of the liquid displaced is equal to the volume of the body.
The weight of the displaced liquid is equal to the upward force exerted on the body.
By measuring the weight of an object in air and then in a liquid, the decrease in weight corresponds to the weight of the displaced liquid.
The weight of the displaced liquid can be calculated using the formula m * g, where g is the acceleration due to gravity.
The gravitational force between two objects is proportional to their masses and inversely proportional to the square of the distance between them.
The acceleration due to gravity is independent of the mass of an object, causing heavy and light objects to fall at the same rate in a vacuum.
The force of gravitation between the Earth and the Sun can be calculated using the formula gm1 m2 / r^2, where m1 and m2 are the masses of the Earth and Sun, and r is the distance between them.

02:08:01

Gravitational Forces and Free Fall Calculations

The text urges to move quickly to the next question about the magnitia of an object on Earth's surface with a mass of 1 kg.
To calculate the gravitational force between objects, the formula F = g * m1 * m2 / r^2 is used, with g remaining constant.
The mass of the object in question is 1 kg, while the mass of the Earth is 6 * 10^24 kg and the radius is 6.4 * 10^6 meters.
The next question involves two stones, one falling from a tower and the other projected upwards with a velocity of 25 m/s, to determine when and where they will meet.
By applying equations of free fall, it is found that the two stones will meet after 4 seconds, with one stone covering 80 meters from the top of the tower.
The next question involves a ball thrown upwards returning to the thrower after 6 seconds, requiring the initial velocity of the throw.
It is determined that the ball takes 3 seconds to reach the top point, with an initial velocity of 30 m/s.
The final question involves a coin dropped from a 49-meter high building, requiring the velocity at which it strikes the ground.

02:24:05

"Physics of Falling Objects Explained Clearly"

A 49-meter long building is used as a reference point for dropping a coin.
The concept of initial velocity being zero when an object is dropped or released is crucial.
The value of acceleration due to gravity (g) is taken as -9.8 meters per second squared.
The formula v = u + 2gh is utilized to calculate the velocity of a falling object.
Homework questions involve determining maximum height, total time of flight, and final velocity before impact.
The process of solving physics problems involving vertical motion is explained, emphasizing the use of key formulas and concepts.

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