(ii) Let t be the time taken by the ball to reach the height 122.5 m, then to calculate t we use the following equation of motion: Therefore, the total time taken by the ball to return = 5 + 5 = 10 s, Hence, the velocity of the stone just before touching the ground is 19.6 ms, R = Average distance between the Earth and the Sun = 1.5 × 10, G = Universal gravitational constant = 6.7 × 10. A sheet of paper has more surface area than a crumpled ball of paper. An apple falls from a tree because of the gravitational attraction between the earth and the apple. But a heavy object does not fall faster than a light object. While swimming why do we feel light? On the other hand, if the density of an object is less than the density of a liquid, then it floats on the surface of the liquid. Answer: Fluids are the substances which can flow e.g., gases and liquids are fluids. Revise the difference between weight and mass. Introduction → Gravitational Force of Earth: If we release a small stone without pushing it from a height, it accelerates towards earth. (b) The principle of lactometer is ‘Archimedes’ principle’. An object immersed in a liquid experiences buoyant force in the vertically upward direction, i.e., in a direction opposite to the weight of the object. 9.8N. Answer: The weighing machine actually measures the weight of the body as the acceleration due to gravity ‘g’ is acting on the body. → The stone is when accelerated towards earth, means some force is acting on it. Is your mass more or less than 42 kg? But the volume of cotton bag is more than the iron bag. State Archimedes’ principle. As pressure is inversely proportional to area, if the area is reduced pressure. All rights reserved. Question 4. Here you can read Chapter 10 of Class 9 Science NCERT Book. Why does formation of tides takes place in sea or ocean? (b) Let the maximum height attained by the ball be h. Initial velocity during the upward journey, u = 29.4 ms -1, Acceleration due to gravity, g = -9.8 m s -2. Answer: The iron rod sinks due to high density and less buoyant force exerted by the water on it, but in case of ship the surface area is increased, the upthrust experienced by the body is more. Class 9 Science NCERT Textbook – Page 142 Concept Insight - A body floats when its weight is lesser than the upward buoyant force acting on it. Application: Answer: Yes, the bottle is attracted downwards by the earth’s gravitational force. Hence density is inversely proportional to volume. Answer: Question 6. Similarly, if the distance is tripled, then the gravitational force becomes one-ninth of its original value. This shows that pressure ∝ 1/area. Question 1. This force produces a uniform acceleration in the objects, which is called acceleration of free fall or acceleration due to gravity. Candidates who are studying in Class 9 can also check Class 9 NCERT Solutions from here. We know that true weight = apparent weight + upthrust. When an object is released from a height such that it falls towards the surface of the Earth under the influence of gravitational force alone, the motion of the object is called free fall. Online test of Chapter 10 Gravitation 3 Science| Class 9th Questions : 1. Can you say which one is heavier and why? Why a truck or a motorbike has much wider tyres? Its dimension is 40 cm x 20 cm x 10 cm. Gravitation Class 9 Extra Questions HOTS (Higher Order Thinking Skills) Question 1. When objects fall towards the Earth under the effect of gravitational force alone, then they are said to be in free fall. (c) Milkman is very honest and trustworthy. The value of acceleration due to gravity. The upward force (buoyant force) acting on the bottle can be reduced by increasing the force on the bottle or by filling the bottle with sand, water etc. Question 1. Questin 1. Give the application of Archimedes’ principle. Question 3. (b). (iii) F is directly proportional to the product of masses of the objects. Answer: The upward force exerted by any fluid (liquid, gas) on an object is known as upthrust or buoyancy. After you have studied lesson, you must be looking for answers of its questions. Chapter wise online tests are given below each chapter heading. (c) … This solution contains questions, answers, images, step by step explanations of the complete Chapter 10 titled Gravitation of Science taught in class 9. Acceleration due to gravity on earth, ge = 9.8 m/s2, Therefore, weight of a 10 kg object on the Earth = 10 × 9.8 = 98 N, Therefore, weight of the same object on the Moon =, Concept Insight Weight of an object on Moon = of the weight of the object on Earth. Gravitation NCERT In Text Solution. Two cork pieces of same size and mass are dipped in two beakers containing water and oil. ∴ The pressure exerted by the box in case (a) is more as compared to the pressure exerted in case (b). Do you feel fascinated or intimidated while studying about gravitation in Physics? A milkman sold his milk in the city and always carried lactometer with him. Question 8. Question 6. The cotton bag is heavier than the iron bar. The Earth attracts the Moon with a force which is same as the force with which the moon attracts the Earth because according to Newton's third law of motion, force of action and reaction are always equal and opposite. The force is along the line joining the centres of two objects. According to the universal law of gravitation, gravitational force between two objects of masses M and m at a distance r from each other is given by: Let mass of the object be represented by m = 1 kg, Universal gravitational constant, G = 6.7 × 10-11 Nm2 kg-2, Since the object is on the surface of the Earth, r = radius of the Earth (R). One cork The density of the substance is more than the density of water (1 g cm, Kindly Sign up for a personalized experience. Answer: The force exerted by a thin and strong string is distributed to very less area and hence the force applied due to the bag is more, the pressure exerted on the body by thin straps will be more and hence will be more painful. Acceleration due to gravity, g = -9.8 ms-2. Question 9. Question 3. Free download links for Class 9 Science NCERT Solutions and UP Board Solutions in PDF format free are given below. If the density of water is 1 gem 3, will the substance float or sink? Mass is the quantity of matter contained in a body. Candidates can click on the subject wise link to get the same. Force or buoyant force acting on a table top by keeping it vertically and horizontally is 19.6.. The substance is 20 cm3 9 Maths and ScienceEducational Loans in India content/service related issues contact!: it means that the force exerted when acts on it give your mobile number below, for any related! Is a device used to find the pressure exerted by fluids on any object immersed in case. 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