# 22 Lecture

## Gravitation

Gravitation is a fundamental force of nature that exists between any two objects with mass. It is responsible for keeping planets in orbit around their stars, and for keeping stars and galaxies together in a larger structure.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

What is the acceleration due to gravity on the surface of the Earth?

A) 9.8 m/s^2

B) 1.6 m/s^2

C) 6.0 m/s^2

D) 5.5 m/s^2

What is the formula for calculating the gravitational force between two objects?

A) F = ma

B) F = G(m1 + m2)

C) F = Gm1m2/r^2

D) F = mgh

Who discovered the law of gravitation?

A) Albert Einstein

B) Galileo Galilei

C) Isaac Newton

D) Johannes Kepler

What is escape velocity?

A) The velocity at which an object falls to Earth

B) The velocity at which an object escapes the gravitational pull of a planet or star

C) The velocity at which an object reaches terminal velocity

D) The velocity at which an object moves in a circular orbit

Answer: B) The velocity at which an object escapes the gravitational pull of a planet or star

A) The radius of the Earth's orbit around the sun

B) The radius of a black hole's event horizon

C) The radius of a planet's atmosphere

D) The radius of a star's core

Which of the following is not a fundamental force of nature?

A) Gravitational force

B) Electromagnetic force

C) Strong nuclear force

D) Weak nuclear force

Answer: E) None of the above

Which planet in our solar system has the strongest gravitational pull?

A) Jupiter

B) Saturn

C) Earth

D) Mars

How does the mass of an object affect its gravitational force?

A) The greater the mass, the greater the gravitational force

B) The smaller the mass, the greater the gravitational force

C) Mass has no effect on gravitational force

D) The effect of mass on gravitational force depends on the distance between objects

Answer: A) The greater the mass, the greater the gravitational force

What is the difference between weight and mass?

A) Weight is a measure of an object's mass, while mass is a measure of the force of gravity on an object

B) Weight is a measure of the force of gravity on an object, while mass is a measure of the amount of matter in an object

C) Weight and mass are two different ways of measuring the same thing

D) Weight and mass are not related to each other

Answer: B) Weight is a measure of the force of gravity on an object, while mass is a measure of the amount of matter in an object

What is the role of dark matter in the study of gravitation?

A) Dark matter has no effect on gravitation

B) Dark matter is responsible for the gravitational pull of galaxies

C) Dark matter is a force that opposes gravity

D) Dark matter is a theoretical construct that has no relation to gravitation

Answer: B) Dark matter is responsible for the gravitational pull of galaxies

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is the formula for gravitational force between two objects?

Answer: The formula for gravitational force between two objects is F = Gm1m2/r^2, where F is the gravitational force, m1 and m2 are the masses of the two objects, r is the distance between them, and G is the gravitational constant.

What is the difference between gravitational force and weight?

Answer: Gravitational force is the force of attraction between any two objects with mass, while weight is the force experienced by an object due to the gravitational pull of a larger object such as a planet or star.

How is planetary motion affected by gravitation?

Answer: Gravitation is responsible for keeping planets in orbit around their stars. The gravitational force acting on the planets causes them to follow a curved path around the star.

What is gravitational lensing?

Answer: Gravitational lensing is the bending of light by the gravitational pull of a massive object such as a galaxy cluster.

What is the theory of general relativity?

Answer: The theory of general relativity, proposed by Albert Einstein, suggests that the force of gravitation is not actually a force, but a curvature of space-time caused by the presence of matter and energy.

What is the significance of the 1919 solar eclipse?

Answer: The 1919 solar eclipse provided the first experimental confirmation of the theory of general relativity, as observations showed that the sun's gravitational field was bending the light from distant stars, just as Einstein had predicted.

What is a black hole?

Answer: A black hole is an object with such a strong gravitational field that nothing, not even light, can escape its pull.

What is the challenge facing theoretical physicists in the study of gravitation?

Answer: The challenge facing theoretical physicists is to reconcile the theory of general relativity with quantum mechanics, which describes the behavior of particles on a very small scale.

How does gravitation affect the behavior of light?

Answer: Gravitation can cause the bending of light around massive objects, which is known as gravitational lensing.

What is the role of gravitation in the universe?

Answer: Gravitation is a fundamental force that is responsible for many of the phenomena we observe in the universe, from the motion of planets to the behavior of light.

### Gravitation

Gravitation is a fundamental force of nature that exists between any two objects with mass. It is responsible for keeping planets in orbit around their stars, and for keeping stars and galaxies together in a larger structure. In this article, we will explore the basic principles of gravitation and its effects on our universe. The theory of gravitation was first proposed by Sir Isaac Newton in the 17th century. He proposed that all objects in the universe are attracted to each other with a force that is directly proportional to their masses, and inversely proportional to the distance between them. This force is known as the gravitational force, and is given by the formula F = Gm1m2/r^2, where F is the gravitational force, m1 and m2 are the masses of the two objects, r is the distance between them, and G is the gravitational constant. One of the most important consequences of gravitation is the phenomenon of planetary motion. In our solar system, the gravitational force between the sun and the planets is responsible for keeping the planets in orbit. According to Newton's laws of motion, an object in motion will continue moving in a straight line unless acted upon by an external force. In the case of planetary motion, the gravitational force acting on the planets causes them to follow a curved path around the sun, rather than a straight line. Gravitational force also has an effect on the behavior of light. Light can be thought of as a wave, and is affected by the curvature of space-time caused by the presence of massive objects. This effect is known as gravitational lensing, and can be observed when light from distant galaxies is bent by the gravitational pull of a massive object such as a galaxy cluster. One of the most important developments in the study of gravitation was Albert Einstein's theory of general relativity. In this theory, Einstein proposed that the force of gravitation is not actually a force at all, but rather a curvature of space-time caused by the presence of matter and energy. According to general relativity, massive objects warp the fabric of space-time around them, causing other objects to follow a curved path around them. The theory of general relativity has been incredibly successful in predicting the behavior of massive objects in the universe. It has been used to explain phenomena such as the orbit of Mercury, the bending of light around massive objects, and the existence of black holes. In fact, the first experimental confirmation of general relativity came in 1919, when observations of a solar eclipse showed that the sun's gravitational field was bending the light from distant stars, just as Einstein had predicted. Despite its successes, the theory of general relativity is not a complete theory of gravitation. It is incompatible with quantum mechanics, which describes the behavior of particles on a very small scale. The development of a theory that can reconcile these two theories is one of the greatest challenges facing theoretical physicists today. In conclusion, gravitation is a fundamental force of nature that is responsible for many of the phenomena we observe in our universe. From the motion of planets to the behavior of light, gravitation has a profound effect on the world around us. While we have made great strides in understanding this force, there is still much to learn about the nature of gravitation and its role in the universe.