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Quick Revision: Gravitation Video Lecture | Science Class 9

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FAQs on Quick Revision: Gravitation Video Lecture - Science Class 9

1. What is the law of universal gravitation?
Ans.The law of universal gravitation states that every mass attracts every other mass in the universe with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This can be expressed mathematically as \( F = G \frac{m_1 m_2}{r^2} \), where \( F \) is the gravitational force, \( G \) is the gravitational constant, \( m_1 \) and \( m_2 \) are the masses, and \( r \) is the distance between their centers.
2. How does gravity affect the motion of planets?
Ans.Gravity is the force that keeps planets in orbit around stars, such as the Earth around the Sun. The gravitational attraction between the Sun and the planets provides the necessary centripetal force that keeps the planets in their elliptical orbits, as described by Kepler's laws of planetary motion.
3. What is the difference between weight and mass in the context of gravity?
Ans.Mass is a measure of the amount of matter in an object, typically measured in kilograms (kg), and does not change regardless of location. Weight, on the other hand, is the force experienced by an object due to gravity and is calculated as the product of mass and gravitational acceleration (Weight = Mass × Gravity). Weight can vary depending on where you are, as gravitational acceleration differs slightly across locations.
4. What role does the gravitational constant (G) play in gravitation?
Ans.The gravitational constant (G) is a key value in the law of universal gravitation, representing the strength of the gravitational force between two masses. Its value is approximately \( 6.674 \times 10^{-11} \, \text{N m}^2/\text{kg}^2 \). It allows us to calculate the gravitational force between two objects based on their masses and the distance between them.
5. How does gravity influence tides on Earth?
Ans.Gravity plays a crucial role in the formation of tides on Earth. The gravitational pull of the Moon and the Sun affects the Earth's oceans, causing them to bulge outwards in the direction of these celestial bodies. This results in high tides in the areas facing the Moon and the Sun, while low tides occur in the areas perpendicular to these. The interaction of gravitational forces and the rotation of the Earth creates the regular cycle of tides.
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