Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board chapter 2 - Work and Energy [Latest edition]

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Explain the difference between potential energy and kinetic energy. 

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Derive the formula for the kinetic energy of an object of mass m, moving with velocity v. 

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Prove that the kinetic energy of a freely falling object on reaching the ground is nothing but the transformation of its initial potential energy. 

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Determine the amount of work done when an object is displaced at an angle of `30^circ` with respect to the direction of the applied force. 

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If an object has 0 momentum, does it have kinetic energy? Explain your answer. 

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Why is the work done on an object moving with uniform circular motion zero? 

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For work to be performed, energy must be ________

(i) transferred from one place to another
(ii) concentrated  
(iii) transformed from one type to another
(iv) destroyed 

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Joule is the unit of ________
(i) force
(ii) work
(iii) power 
(iv) energy 

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Which of the forces involved  in dragging a heavy object on a smooth, horizontal surface, have the same magnitude? 
(i) the horizontal applied force
(ii) gravitational force
(iii) reaction force in vertical direction
(iv) force of friction  

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Power is a measure of the _______
(i) the rapidity with which work is done
(ii) amount of energy required to perform the work
(iii) The slowness with which work is performed
(iv) length of time

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While dragging or lifting an object, negative work is done by ________
(i) the applied force
(ii) gravitational force
(iii) frictional force  
(iv) reaction force 

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The potential energy of your body is least when you are _____________

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The total energy of an object falling freely towards the ground ___________

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If we increase the velocity of a car moving on a flat surface to four times its original speed, its potential energy ____________

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The work done on an object does not depend on _______

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An electric pump has 2 kW power. How much water will the pump lift every minute to a height of 10 m?

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If a 1200 W electric iron is used daily for 30 minutes, how much total electricity is consumed in the month of April?

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If the energy of a ball falling from a height of 10 metres is reduced by 40%, how high will it rebound?

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The velocity of a car increase from 54 km/hr to 72 km/hr. How much is the work done if the mass of the car is 1500 kg?

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Ravi applied a force of  10 N and moved a book 30 cm in the direction of the force. How much was the work done by Ravi?