Case I Where K.E. We have Provided Work and Energy Class 9 Science MCQs Questions with Answers to help students understand the concept very well. Hence, work is done by wind on the boat. Work done by force is equal to the change in kinetic energy. The kinetic energy of a body is the energy possessed by the body by virtue of its motion. Therefore, its kinetic energy becomes 4 times its original value, because it is proportional to the square of the velocity. Hence, 20.8 x 104 J of work is required to stop the car. work done by force = (Ek)2 – (Ek)5 Objects in motion possess energy, we call this energy kinetic energy. So the kinetic energy at rest should be zero. When an object falls freely towards the ground, its potential energy decreases and kinetic energy increases. are solved by group of students and teacher of Class 9, which is also the largest student community of Class 9. Q73: (a) Derive an expression to calculate the kinetic energy of a body. (ii) There is a displacement of the body by the application of force in or opposite to the direction of force. Kinetic energy depends upon the velocity and the mass of the body. Physics. Q8 : Does the transfer of energy take place when you push a huge rock with all your might and fail to move it? W= mgh Kinetic energy is a property of a moving object or particle and depends not only on its motion but also on its mass. h= Vertical displacement = 0 1 Answer +1 vote . as = 1/2 v 2. Write an expression for the kinetic energy of an object. m is the mass of the body. We have Provided Work and Energy Class 9 Science MCQs Questions with Answers to help students understand the concept very well. Whileriding a bicycle, the muscular energy of the rider gets transferred into heat energy and kinetic energy of the bicycle. Derive an expression for kinetic energy of an object. Q15 : Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. m is the mass of … A body can do different amount of work in different time intervals. m= Mass of the object 1 kWh = 3.6 x 106 J Consider the case of an oscillating pendulum. is done on EduRev Study Group by Class 9 Students. During the transformation, the total energy remains conserved. Work and Energy Class 9 MCQs Questions with Answers. = ½ mv 2. (a) Energy possessed by a body due to its motion is called its kinetic energy.Kinetic energy is directly proportional to the mass and square of the velocity of the moving body. (i) Kinetic energy when the object was moving with a velocity 5 m s -1 No. Velocity of car, v= 60 km/h answered Jul 8 by KomalKumari (48.9k points) selected Jul 8 by Amrita01 . Question 8. What will be its kinetic energy when its velocity is doubled? Hence, the acceleration of the object is zero. It can only be converted from one form to another. Q 8. Q13 : A person holds a bundle of hay over his head for 30 minutes and gets tired. 1 unit = 1 kWh Do you agree with her? Q14 : An electric heater is rated 1500 W. How much energy does it use in 10 hours? In fact, kinetic energy of an object moving with a certain velocity is equal to the work done to make it acquire that velocity. As the object touches the ground, all its potential energy gets converted into kinetic energy. Question 1. This energy is dependent on the velocity of the object squared. Therefore, its kinetic energy becomes 4 times its original value, because it is proportional to the square of the velocity. (i) A force acts on the body. Here, the force causes a displacement. "Energy posses by a body by virtue of its motion is referred to as 'Kinetic Energy'". Hence, it is better to define average power. Hence, 2100 J of work is done in ploughing the length of the field. Work done = Energy consumed by the lamp = 1000 J Kinetic energy is given by the expression, Where, = Kinetic energy of the object moving with a velocity, v. m= Mass of the object (i) Kinetic energy when the object was moving with a velocity 5 m s −1. How much work is done in ploughing the length of the field? Kinetic energy, form of energy that an object or a particle has by reason of its motion. Work, Power And Energy Class 9 Extra Questions Short Answer Type 2. What happens to its kinetic energy? Solution: Kinetic energy of an object, K.E. Q9 : The kinetic energy of an object of mass, m moving with a velocity of 5 m s-1 is 25 J. Kinetic energy is given by the expression, Where, = Kinetic energy of the object moving with a velocity, v m= Mass of the object (i) Kinetic energy when the object was moving with a velocity 5 m s -1 (ii) Kinetic energy when the object was moving with a velocity 2 m s-1 … Answer: Vertical displacement is given by the difference in the initial and final positions/heights of the object, which is zero. Q3. Q16 : An object of mass, mis moving with a constant velocity, v. How much work should be done on the object in order to bring the object to rest? Write an expression for the kinetic energy of an object. Question 2 Page 152 - Chapter 11 Class 9 - Work and Energy. Classically, kinetic energy is related to mass and speed by the familiar expression K = 1 2 m u 2. W= F ÃƒÆ’Ã¢â‚¬” S W = mg x 0 = 0 J Where K.E. Also, there is no loss of energy because muscular energy is transferred into heat energy, which causes our body to become hot. How much energy is this in joules? Write an expression for the kinetic energy of an object. 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. The kinetic energy of an object of mass, m moving with a velocity of 5 ms-1 is 25 J. Hence, work is done by the wind mill in lifting water from the well. Case II Obtain an expression for the kinetic energy of an object. Q4 : Write an expression for the work done when a force is acting on an object in the direction of its displacement. Answer : Sol. Required fields are marked *. When a force F displaces a body through a distance S in the direction of the applied force, then the work done Won the body is given by the expression: moving object possesses kinetic energy. Mass of car, m= 1500 kg Expression for kinetic energy is K E = 1/2mv 2. Hence, the total energy of the pendulum and the surrounding system remain conserved. Where, The initial and the final points of the path of the object lie on the same horizontal line. (i) A force acts on the body. Answer : Justify your answer. • A sailboat is moving due to wind energy. Answer: Expression for kinetic energyis m = Mass of the object v = Velocityof the object = 5 m s−1 Given that kinetic energy, = 25 J (i) If the velocityof an object is doubled, then v = 5 × 2 = 10 m s−1. (g)Wind energy applies a force on the sailboat to push it in the forward direction. Therefore, Suma swims in the forward direction caused by the forward reaction of water. K 1 =mv 1 2 /2. The kind of motion may be translation, rotation about an axis, vibration, or any combination of motions. 7)A falling coconut, running athlete possesses kinetic energy. The mechanical energy (kinetic energy + potential energy) of a freely falling object remains constant. Hence, kinetic energy = 25 x 4 = 100 J. derive equation for loss of kinetic energy in case of a completely inelastic collision in one dimension - Physics - TopperLearning.com | 98uzboee Answer : This is because when the body falls from a height, then its potential energy changes into kinetic energy progressively. Kinetic energy when the object was moving with a velocity 2 m s −1. Kinetic energyof hammer is used in driving a nail into a log of wood, kinetic energy of air is used to run wind mills, etc. 2. If the line joining A and B is horizontal, what is the work done on the object by the gravitational force? It can also deform the ground depending upon the nature of the ground and the amount of kinetic energy possessed by the object. Answer : Answer : as = 1/2 v 2. Where is the energy you spend going? Q12 : Can there be displacement of an object in the absence of any force acting on it? Calculate the work done by the force. Where, It is moved to a point B. It is further classified into gravitational potential energy (GPE) and elastic potential energy … Q2 : An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. Answer : For example, a fast moving pebble can injure a person or break glass pane of window, energy of moving vehicle, a fast moving wind can damage many house, or wind can move blades of wind mill, etc. Therefore, the law of conservation of energy is not violated. Question From class 9 Chapter WORK AND ENERGY Write an expression for kinetic energy of an object. When a pendulum moves from its mean position P to either of its extreme positions A or B, it rises through a height h above the mean level P. At this point, the kinetic energy of the bob changes completely into potential energy. 9 - work and energy Class 9 - work and energy Class 9 which. Mechanical energy ( kinetic energy of an object of mass, m moving a... The energy in kW h consumed in 10 hours by 3 rd eq n of motion, 2. 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