Gravitation and Free Fall Test paper-1
Download File Gravitation and Free Fall E-Notes Full Download File 9th gravitation Solved Questions-1 Download File 9th gravitation Solved Questions-2 Download File 9th gravitation Solved Numerical Download File |
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Topics: Thrust, Pressure, Buoyancy and Archimedes Principal and Density
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CHapter oveview |
Gravitation and Floatation
In this chapter, we'll dive into the fascinating world of gravity and how objects float or sink in fluids. Let's break down the key concepts step by step: 1. Gravitation: Pull of the Earth - Everything on Earth experiences a force called gravity, which pulls objects towards its center. - Sir Isaac Newton explained gravity with his famous law of universal gravitation. It states that every object attracts every other object with a force that is directly proportional to their masses and inversely proportional to the square of the distance between them. - Weight is the force with which an object is pulled due to gravity. It depends on the mass of the object and the acceleration due to gravity. 2. Free Fall and Acceleration Due to Gravity - When an object falls under the influence of gravity alone, it is said to be in free fall. - The acceleration due to gravity on the surface of the Earth is approximately 9.8 m/s². This means that the velocity of a falling object increases by 9.8 meters per second every second. 3. Fluid Pressure and Buoyancy = vdg - Fluids exert pressure in all directions. This is why things feel lighter when immersed in fluids. - Archimedes' principle explains buoyancy: an object immersed in a fluid experience an upward buoyant force equal to the weight of the fluid displaced by the object. 4. Floatation and Density - An object will float if its density is less than the density of the fluid it's placed in. - The buoyant force acting on an object determines whether it will float, sink, or remain suspended in a fluid. - We can calculate density using the formula: Density = Mass / Volume. 5. Thrust and Pressure in Fluids - Thrust is the force exerted on an object by a fluid, often due to fluid pressure differences. - Pressure is the force per unit area. It is calculated using the formula: Pressure = Force / Area. 6. Applications of Buoyancy - Buoyancy has various real-world applications, such as in hot air balloons, submarines, and ships. 7. Gravitational Force and Motion of Planets - The gravitational force between the Sun and planets keeps them in their orbits. - Kepler's laws of planetary motion provide insights into the movement of planets. 8. Universal Law of Gravitation and Weightlessness - The universal law of gravitation is applicable not only on Earth but also throughout the universe. - Astronauts experience weightlessness in space because they are in free fall around the Earth. Remember, understanding these concepts will help you appreciate the forces that shape our everyday experiences, from the way we stay grounded on Earth to the marvels of space exploration. Feel free to explore further using educational resource provided by J Sunil Sir, and don't hesitate to ask if you have any questions or need more detailed explanations! |
Solved Questions |
Question: Two balls of different masses are thrown vertically upwards with same initial speed. Which one of them will rise to the greater height?
Answer: Both will reach the same maximum height at the same instant, because they will have the same acceleration due to gravity Question: What are Laws of Planetary Motion? Ans: Kepler's three laws of planetary motion can be described as follows: The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus. (The Law of Orbit) An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time. (The Law of Equal Areas) The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of periods) T2/R3 ratio is the same Question: Derive the inverse square of Newton. We can derive Newton's law of gravitation from Kepler's third law. Kepler's Third Law can be written as T2 = kr3 or T2 = (4π2/GM).r3 ..............(1) now, we know that the time period, T = 2πr/v, so (1) becomes (2πr/v)2 = (4π2/GM).r3 or 4π2 (r/v)2 = (4π2/GM).r3 or (r/v)2 = (1/GM).r3 = r3/GM .......................(2) we know that, centripetal acceleration a = v2/r [from ma = mv2/r] Thus, equation (2) becomes r/a = r3/GM or 1/a = r2/GM or a = GM/r2 .......................... (3) and we also know that F = ma, thus using equation (3) we would get F = ma = m(GM/r2) Thus, we have derived the Newton's Law of Gravitation, which is F = GMm/r 2 from Kepler's Third Law Question: When we move from the poles to the equator. Hence, the value of ‘ g ’ decreases. Why Ans: The shape of earth is an ellipse so when we move from the poles to the equator the radius of the earth R increases. Hence, the value of ‘ g ’ decreases because value 'g' is inversely proportional to the radius of earth. g = GM/R2 Question: What is the difference between centrifugal force and centripetal force? Ans: Centripetal Force (i) It is the force that keeps a body in circular path. (ii) It acts toward the center. Centrifugal Force (i) It is the pseudo force that tries to make a body fly off the circular path. (ii) It acts outward the center. Question: Explain: Centrifugal force and Centripetal force? Ans: A force which is required to move a body uniformly in a circle is known as centripetal force. This force acts along the radius and towards the center of the circle, Centrifugal force arises when a body is moving actually along a circular path, by virtue of tendency of the body to regain its natural straight-line path. This force acts along the radius and away from the center of the circle. The Centripetal force formula is given by Fc = mv^2/r Question: Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object? Ans: This is because acceleration is inversely proportional to mass. Since mass of heavy of is greater it accelerates slower than lighter object. This is why a heavy object does not fall faster than a light object? Question: The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why? Ans: The earth attracts the moon with equal force with which the moon attracts the earth. This because , according to Newton’s third law of motion “to every action there is equal reaction Question: If the moon attracts the earth, why does the earth not move towards the moon? Ans: This is because acceleration is inversely proportional to mass. The earth is much larger than the moon so, the acceleration produced on the earth surface cannot be noticed. Question: What is aphelion and perihelion? Ans: The aphelion is the point in the orbit of an object where it is farthest from the Sun. The point in orbit where an object is nearest to the sun is called the perihelion. The word aphelion derives from the Greek words, apo meaning away, off, apart and Helios (the Greek god of the sun). |
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