Kinetic energy when the object was moving with a velocity 2 m s −1. Q3 : When do we say that work is done? Kinetic energy of an object of mass, mmoving with a velocity, vis given by the expression, (ii) There is a displacement of the body by the application of force in or opposite to the direction of force. Its SI unit is Joule (J). Answer: Download free PDF of best NCERT Solutions , Class 9, Physics, CBSE- Work and Energy . Heat energy heats the rider’s body. The unit of energy is the same as that of energy. The kinetic energy of a body is the energy possessed by the body by virtue of its motion. Answer : Classically, kinetic energy is related to mass and speed by the familiar expression K = 1 2 m u 2. What is the work done by the force of gravity on the object? 1 kWh = 3.6 x 106 J Answer : the kinetic energy formula derivation can be done using algebra and calculus. When a bulb is connected to a battery, then the chemical energy of the battery is transferred into electrical energy. Q11 : Define 1 watt of power: The kinetic energy derivation using only algebra is one of the best ways to understand the formula in-depth. All Rights Reserved. Q3 : A battery lights a bulb. Therefore, there is a displacement in the boat in the direction of force. Hence, the acceleration of the object is zero. Hence, the work done on the satellite by the Earth is zero. The law of conservation of energy is not violated because the energy lost by the pendulum to overcome friction is gained by its surroundings. Unit of Energy: Unit of energy is same as that of the unit of work. (i) A force acts on the body. Give three examples when the object is not displaced in spite of a force acting on it. Physics. K = 1 2 m u 2. W = mg x 0 = 0 J S= 8 m 1 kWh = 3.6 x 106 J Both the methods are explained below. What will be its kinetic energy when its velocity is doubled? What is its potential energy? = ½ mv 2. NCERT Solutions for Class 9 Science Chapter 11 PDF: Work and Energy chapter deals with concepts of conservation of energy, its types, and how work & energy are interrelated. Q3. NCERT DC Pandey Sunil Batra HC Verma Pradeep Errorless. v 2 = 2as. Derivation : We know that, W = f x s but f = ma. Sol. Question 1. (i) A force acts on the body. Students must understand the kinetic energy derivation method properly to excel in their examination. NCERT Textbook for Class 9 Science – Page 152 Q1. Therefore we can say that kinetic energy is: Derivation of Kinetic Energy using Calculus. Question 7. Answer : 1 Answer +1 vote . When a person holds a bundle of hay over his head, then there is no displacement in the bundle of hay. • A donkey is carrying a load on its back. The initial and the final points of the path of the object lie on the same horizontal line. Kinetic energy, form of energy that an object or a particle has by reason of its motion. = where m = mass of the object and v = uniform velocity of the object. = 0.50 x 10 = 5 kWh This process is repeated as long as the pendulum oscillates. Where, Question : Solutions of Questions on Page Number : 148, Q1 : A force of 7 N acts on an object. Therefore, 250 units of energy = 250 x 3.6 x 106 = 9 x 108 J, Q10 : A certain household has consumed 250 units of energy during a month. The kinetic energy becomes zero, and the bob possesses only potential energy. is the kinetic energy. Energy consumed by an electric heater can be obtained with the help ofthe expression, Q21 : A freely falling object eventually stops on reaching the ground. NCERT Textbook for Class 9 Science – Page 152 Q1. as = 1/2 v 2. Hence, the work done is zero during the process of food grains getting dried in the Sun. Power is given by the expression, The kinetic energy of an object of mass, m moving with a velocity of 5 m s-1 is 25 J. Work and Energy Class 9 MCQs Questions with Answers. An important topic of NCERT Solutions for Class 9 Science Chapter 11 is : Energy: Energy is the capability of doing work. Question From class 9 Chapter WORK AND ENERGY Write an expression for kinetic energy of an object. Kinetic energy - The energy possessed by virtue of its motion is said to be kinetic energy. 11.3). Work is done whenever the given conditions are satisfied: Hence, Soni is right. Although, force of gravity is acting on the bundle, the person is not applying any force on it. Has he done some work or not? m is the mass of the body. Work done by the force of gravity on an object depends only on vertical displacement. at rest, u=0. answered Jul 8 by KomalKumari (48.9k points) selected Jul 8 by Amrita01 . Now rearranging the differential terms to get the function and the integral into an agreement. Hence, the energy consumed by the heater in 10 h is 15 kWh. Given that kinetic energy, = 25 J Q72: Define kinetic energy. Work and Energy Kinetic Energy . Suppose an object is moving with constant velocity. But, displacement of the load is in the forward direction. Kinetic Energy Formula (Rotational) The rotational kinetic energy equation goes like this: K = (1/2) Iw 2 (It is the Rotational kinetic energy of an object with Moment of inertia I and angular velocity w) Types of Kinetic Energy. A body is said to have power of 1 watt if it does work at the rate of 1 joule in 1 s, i.e., Q12 : A lamp consumes 1000 J of electrical energy in 10 s. What is its power? Hence, kinetic energy = 25 x 4 = 100 J. Is it a violation of the law of conservation of energy? Where, Q 7. Through these solutions, we bring you the best in industry solutions for NCERT chapter 11 Class 9 science textbook question. Work done = Energy consumed by the lamp = 1000 J This is the formula of Kinetic energy of an object of mass m moving with speed v along a line. So the kinetic energy at rest should be zero. Write an expression for kinetic energy of an object. A body of mass 25 g has a momentum of 0.40 kgm/s.Find its kinetic energy. All NCERT textbook questions have been solved by our expert teachers. 6)A moving bus,car,falling stone possesses kinetic energy. How much energy is this in joules? K 2 = m.v 2 2 /2, is the final Kinetic energy of the object, and the quantity. Why? It comes to rest because air resistance resists its motion. = Kinetic energy of the object moving with a velocity, v Q2. Q7 : What is the kinetic energy of an object? The kinetic energy of a body is the energy that it possessed due to its motion. Work, Power And Energy Class 9 Extra Questions Short Answer Questions-II. • An engine is pulling a train. (i) A force acts on the body. Hence, the energy consumed by four equal rating devices in 10 h will be 4 x 5 kWh = 20 kWh = 20 Units. Q6 : A pair of bullocks exerts a force of 140 N on a plough. Kinetic energy is the energy possessed by an object because of motion. Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass. derive equation for loss of kinetic energy in case of a completely inelastic collision in one dimension - Physics - TopperLearning.com | 98uzboee 1 unit of energy is equal to 1 kilowatt hour (kWh). v is the velocity with which body is moving. The corresponding relativistic expression for kinetic energy can be obtained from the work-energy theorem. Write an expression for the kinetic energy of an object. It can also deform the ground depending upon the nature of the ground and the amount of kinetic energy possessed by the object. Q16 : An object of mass, mis moving with a constant velocity, v. 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