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Questions and Answers
What is the value of g at the height of Mount Everest (8.8 km)?
What is the value of g at the height of Mount Everest (8.8 km)?
How does the value of g change when you go deeper inside the Earth?
How does the value of g change when you go deeper inside the Earth?
At what height is the value of g approximately 0.225 m/s²?
At what height is the value of g approximately 0.225 m/s²?
What will be the value of g at the center of the Earth?
What will be the value of g at the center of the Earth?
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How does the mass of an object change when moving from Earth to the moon?
How does the mass of an object change when moving from Earth to the moon?
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Using the same amount of force, how much higher can you jump on the moon compared to the Earth?
Using the same amount of force, how much higher can you jump on the moon compared to the Earth?
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What is the SI unit of mass?
What is the SI unit of mass?
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What is the measure of inertia of an object?
What is the measure of inertia of an object?
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Which statement is true about the weight of an object?
Which statement is true about the weight of an object?
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What does a weighing machine in a shop actually measure?
What does a weighing machine in a shop actually measure?
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What is the direction of the gravitational force between two objects?
What is the direction of the gravitational force between two objects?
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What is the nature of the gravitational force compared to other fundamental forces?
What is the nature of the gravitational force compared to other fundamental forces?
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What is the formula for the gravitational force between two objects?
What is the formula for the gravitational force between two objects?
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What is the region around an object where the gravitational force can be detected?
What is the region around an object where the gravitational force can be detected?
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What is the energy an object has due to its position within a gravitational field?
What is the energy an object has due to its position within a gravitational field?
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What is the unit of the gravitational constant G?
What is the unit of the gravitational constant G?
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Study Notes
Kepler's Laws
- Planetary motion follows three laws described by Johannes Kepler, known as Kepler's laws
- Kepler's laws were derived from studying data on planetary positions and motion
- Kepler's First Law: The orbit of a planet is an ellipse with the Sun at one of the foci
- Kepler's Second Law: The line joining the planet and the Sun sweeps equal areas in equal intervals of time
- Kepler's Third Law: The square of the period of revolution of a planet is directly proportional to the cube of the mean distance of the planet from the Sun
Newton's Universal Law of Gravitation
- Newton formulated his theory of Universal Gravity, which states that every object in the Universe attracts every other object with a definite force
- The force is directly proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between them
- The gravitational force can be expressed mathematically as F = G * (m1 * m2) / d^2, where G is the Universal Gravitational constant
Introduction to Scientists
- Johannes Kepler (1571-1630) was a German astronomer and mathematician who discovered Kepler's laws
- Sir Isaac Newton (1642-1727) was an English scientist who formulated Newton's laws of motion and the law of Universal Gravitation
Force and Motion
- A force is necessary to change the speed or direction of motion of an object
- Newton's laws of motion and the law of Universal Gravitation help explain the behavior of objects on Earth and in the Universe
Circular Motion and Centripetal Force
- An object moving in a circle experiences a force directed towards the centre of the circle, known as the centripetal force
- The centripetal force is necessary to keep the object moving in a circle and not flying off in a straight line
- Examples of circular motion include the moon orbiting the Earth and the Earth orbiting the Sun
Gravitation
- Gravitation is a universal force that acts between all objects with mass
- The force of gravitation is responsible for the motion of planets, stars, and galaxies
- The force of gravitation is also responsible for the falling of objects on Earth
Centripetal Force and Uniform Circular Motion
- The centripetal force is related to the speed and radius of the circle by the equation F = m * v^2 / r
- The force of gravitation provides the centripetal force necessary for uniform circular motion
- The speed of an object in uniform circular motion can be expressed in terms of the period of revolution and the radius of the circle
Solved Examples
- Example 1: Calculating the gravitational force between two objects
- Example 2: Calculating the velocity of an object in uniform circular motion### Mahendra's Acceleration
- Mahendra's mass is 75 kg, and the force applied to him is 733 N.
- Mahendra's acceleration is calculated as 9.77 m/s² using the formula a = F/m.
- After 1 second, Mahendra's velocity is 9.77 m/s.
Newton's Law of Gravitation
- Every object attracts every other object with the same force.
- The gravitational force due to the earth acts on the moon and artificial satellites, causing them to orbit the earth.
Earth's Gravitational Acceleration
- The earth exerts a gravitational force on objects near it, resulting in acceleration.
- This acceleration is called acceleration due to gravity, denoted by 'g', and is directed towards the center of the earth.
- The value of g on the surface of the earth is 9.77 m/s².
Value of g on the Surface of the Earth
- The value of g can be calculated using Newton's universal law of gravitation.
- The formula for g is g = GM/r², where G is the gravitational constant, M is the mass of the earth, and r is the distance from the center of the earth.
- The value of g on the surface of the earth is 9.77 m/s².
Variation in Value of g
- The value of g changes along the surface of the earth due to the earth's slightly ellipsoidal shape.
- The value of g is highest at the poles (9.832 m/s²) and lowest at the equator (9.78 m/s²).
- The value of g also changes with height, decreasing as the distance from the center of the earth increases.
- The value of g changes if we go inside the earth, decreasing as the distance from the center of the earth decreases.
Change of g with Height and Depth
- The value of g decreases with increasing height, but the decrease is small for heights compared to the earth's radius.
- The value of g also changes with depth, decreasing as we go deeper inside the earth.
Mass and Weight
- Mass is the amount of matter present in an object, measured in kilograms (kg).
- Mass is a scalar quantity and does not change, even when going to another planet.
- Weight is the force with which the earth attracts an object, measured in Newtons (N).
- Weight is a vector quantity and changes from place to place, depending on the value of g.
- Colloquially, weight is often used to refer to mass, but scientifically, weight refers to the gravitational force on an object.
Universal Gravitation
- Gravity is a universal force, acting between every point mass, attracting them to each other along the line intersecting both points.
- This force is a two-way interaction, where both objects attract each other with the same force, but in opposite directions.
- Compared to other fundamental forces, gravity is much weaker, but it can act over vast distances, even across millions of kilometers.
Gravitational Forces
- The gravitational force (F) between two objects is calculated by the equation: F = G * (m1 * m2) / r^2, where G is the gravitational constant (6.67408e-11 N*m^2/kg^2).
- The masses of the two objects are represented by m1 and m2, and r is the distance between their centers.
- A gravitational field is a region around an object where the gravitational force can be detected, and it is a vector field surrounding every object with mass.
- Gravitational potential energy (U) is the energy an object has due to its position within a gravitational field, calculated by the equation: U = m * g * h.
- The variables in this equation are the mass of the object (m), the acceleration due to gravity (g, approximately 9.8 m/s^2 on Earth), and the height of the object above the ground (h).
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Description
Learn about the three laws of planetary motion described by Johannes Kepler, including the shape of planetary orbits and their motion.