## Sunday, 9 November 2014

### Chapter 11. Work and Energy - Science | MCQ - Multiple Choice Questions | CBSE Class 9th

Question 1. A dog weighing 25 kg, while chasing a cat, jumps over a fence of height 1.6 m. What is the potential energy of dog at the top of fence ?
(Take gravity due to earth 'g'=10 m s-2 )

(a) 160 Joules
(b) 320 Joules
(c) 380 Joules
(d) 480 Joules

Question 2. In winters, rubbing of hands together for some time, causes a sensation of warmth mainly because of

(a) heat caused by the force of friction
(b) heat caused by the momentum
(c) heat caused by the motion
(d) heat flows from the blood to skin

Answer. (a) heat caused by the force of friction

Question 3. A soldier makes a swing jump between two points, by holding one end of a rope, other end of which is tied to some higher point. Work done by rope in jumping of soldier from one point to another is an example of :

(a) Negative work
(b) Positive work
(c) Zero work done
(d) None of the above

Question 4. Which of the following does not have unit as Joule?

(a) Work done
(b) Kinetic energy
(c) Potential energy
(d) Force

Question 5 . The commercial unit of energy consumption in households, industries and commercial establishments is

(a) Joule
(b) Watt
(c) kW
(d) KW h (kilowatt hour)

Answer. (d) KW h (kilowatt hour)

Question 6. A runner, while moving, is facing a wind from the opposite direction. The work done by the wind on runner will be

(a) Zero
(b) negative
(c) Positive
(d) infinity

Question 7. The value of 1 Kilo Watt Hour is

(a) 1.8 X 105J
(b) 3.6 X 106J
(c) 5.4 X 108J
(d) 7.2 X 1010J

Question 8. An external force is being applied on an object at some angle and it causes the object either to be pulled or pushed on a rough surface. Which of the following holds true ?

(a) It is easier to push the object
(b) It is easier to pull the object
(c) It requires same efforts to push or pull the object
(d) None of the above

Question 9. A car with mass ‘M’ is moving on horizontal road with velocity ‘v’. Driver applies accelerator and increases it speed 3 times to ‘3v’. The final K.E. acquired by the car will be :

(a) 1.5 Mv2
(b) 2.5 Mv2
(c) 3.5 Mv2
(d) 4.5 Mv2

Question 10. As per the statement given in Q.9 above, What change it will take place for the potential energy of the car

(a) It will remain the same
(b) It will increase
(c) It will decrease
(d) It will becomes 3 times the Intial P.E.

Answer. (a) It will remain the same

Chapter 11. Work and Energy - Science (Physics) | Multiple Choice Questions (MCQs) | CBSE Class 9th

Question 11. As per the statement of Q.9, the amount of addition work done by the car, after applying the accelerator, is

(a) 1.5 Mv2
(b) 2.5 Mv2
(c) 3.5 Mv2
(d) 4 Mv2

Question 12. In first case, a force of 5 N is applied on a object for 6 minutes and displaces it by 10 meters. In second case, A force of 10 N is applied on the same object for 3 minutes and displaces it by 5 meters. In which case there is more work done?

(a) First case
(b) Second case
(c) In both cases, work done is same
(d) In both cases, work done is zero

Answer. (c) In both cases, work done is same

Question 13. A cyclist is moving at a speed of 5 m/s on leveled road. While going down the slop, his speed increases to 7 m/s. Here the nature of work done by gravitational force in increasing the speed of cyclist is an example of ?

(a) positive work done
(b) negative work done
(c) Infinite work done
(d) Zero work done

Question 14. The person will have maximum Potential Energy, when ?

(a) he is sleeping on the ground
(b) he is sitting on the ground
(c) he is sleeping on the bed
(d) he is standing on the roof

Answer. (d) standing on the roof

Question 15. When we stretch a rubber band, the Elastic Potential Energy of rubber band

(a) remains unchanged
(b) becomes zero
(c) increases
(d) decreases

Question 16. Expression for Power of an object is equal to:

(a) Power = Work done X Time
(b) Power = Time/ Work done
(c) Power = Work done/Time
(d) Power = Force X Displacement

Answer. (c) Power = Work done/Time

Question 17. When a body falls freely towards the earth then the total energy

(a) remains constant
(b) increases
(c) decreases
(d) first increases and then decreases

Question 18. In hydro electricity generation, water stored in a dam possesses:

(a) electrical energy
(b) chemical energy
(c) thermal energy
(d) potential energy

Question 19. When a body slides down on an inclined surface, which holds true ?

(a) It has no energy
(b) It has potential energy only
(c) It has kinetic energy only
(d) It has both kinetic and potential energy

Answer. (d) It has both kinetic and potential energy

Question 20. According to the law of conservation of energy, which of the statements given below is correct ?

(a) Energy can not be transformed from one form to another
(b) It can be created or destroyed.
(c) The total energy before and after the transformation always remains constant.
(d) The total energy before and after the transformation is always different.

Answer. (c) The total energy before and after the transformation always remains constant.

Work and Energy - Physics | Multiple Choice Questions (MCQ) | CBSE Class 9th Science

Question 21. An object is displaced by 10 meters in the direction of applied force. If the applied force is 75 N, What is the work done by the force?

(a) 0.75 Joule
(b) 7.5 Joule
(c) 75 joule
(d) 750 joule

Question 22. An object is subjected to free fall from height 'h' to ground. At mid point of its fall i.e. at 1/2 of height H, it will acquire?

(a) more kinetic and less potential energy
(b) less kinetic and more potential energy
(c) same kinetic and potential energy
(d) only potential energy

Answer. (c) same kinetic and potential energy

Question 23. An object is thrown vertically upward and it reaches to a maximum height 'h' from the ground. During its flight, on reaching 3/4 of height H, it will acquire?

(a) less potential and high kinetic energy
(b) more potential and less kinetic energy
(c) same potential and kinetic energy
(d) only kinetic energy

Answer. more potential and less kinetic energy

Question 24. In a construction site, a crane lifts 1000 kg of concrete mix to roof top at a height of 20 meters in 50 seconds. If the value of gravity 'g' due to earth is 10 m s-2, the power of elevator will be..

(a) 2 KW
(b) 3 KW
(c) 4 KW
(d) 5 KW

Question 25. A body is moving with velocity 4 m/s , possesses 56 Joules of Kinetic Energy. The momentum of body will be equal to

(a) 7 kgms-1
(b) 14 kgms-1
(c) 21 kgms-1
(d) 28 kgms-1

Question 26. Which of the following is correct?

(a) A fruit hanging from the tree possesses gravitational potential energy
(b) A running player acquires Kinetic Energy
(c) A piston with compressed air contains potential energy
(d) All of the above

Answer. (d) All of the above

Question 27. A vector quantity has both magnitude as well as direction, where as a scalar quantity has only magnitude and no direction. which of the given below is a scalar quantity?

(a) Velocity
(b) Force
(c) Work done
(d) Momentum

Question 28. In Force vs Displacement graph, What does the area under the curve represents :

(a) Velocity
(b) Acceleration
(c) Force
(d) Work done

Question 29. For an object of mass 'm', falling freely from height 'h', under acceleration due to gravity 'g', If v is the velocity of the object at a given instant, then during the course of its fall, for all points, which of the expression given below is correct ?

(a) mgh > 1/2 mv2
(b) mgh < 1/2 mv2
(c) mgh = 1/2 mv2
(d) mgh + 1/2 mv2 = Constant

Answer. (d) mgh + 1/2 mv2 = Constant

Question 30. According to the law of conservation of energy,

(a) Energy can only be transformed from one form to another
(b) It can neither be created nor destroyed
(c) The total energy before and after the transformation always remains constant
(d) All of the above

Answer. (d) All of the above

CBSE Class 9th | Science | Multiple Choice Questions (MCQ) | Chapter 11. Work and Energy - (Physics)

Question 31. According to standard definition of Work done, when the force 'F' acts on the object and object is displaced through a distance 's' in the direction of the force, then work done by a force is equal to

(a) W = F/s
(b) W = s/F
(c) W = F × s
(d) W = Zero

Answer. (c) W = F × s

Question 32. 1 J is the amount of work done on an object when a force of 1 N displaces it along its line of action by :

(a) 1 cm .
(b) 1 m
(c) 100 m
(d) 1 km

Question 33. A joule (J) is used as a unit of measurement for :

(a) Kinetic Energy
(b) Potential Energy
(c) Work done
(d) All of the above

Answer. (d) All of the above

Question 34. Power of an agent is

(a) the rate of generation of energy .
(b) the rate of transfer of energy
(c) the rate of consumption of energy
(d) the rate of work done
(e) All of the above

Answer. (e) All of the above

Question 35. Newton meter per second or 1 joule/second or 1 watt is unit of

(a) Force
(b) Work
(c) Power
(d) Energy

Question 36. When a spring is compressed or stretched beyond its natural position by applying some force, work is done on it. Its elastic potential energy

(a) increases
(b) Decreases
(c) Disappears
(d) Does not change

Question 37. As a person climbs up from ground floor of the building to higher floor, The potential energy of person on the higher floor, relative to the ground floor, can be expressed as

(a) the work done in lifting his weight from ground floor to higher floor.
(b) the product of his weight and the distance between the ground and higher floor.
(c) the energy the person because of his position above the ground floor.
(d) Any one of the above

Answer. (d) Any one of the above

Question 38. A car which is 8 times heavier than a motorcycle is moving at a speed which is just 1/2 the speed of motorcycle. . The amount of work done required to stop the car as compare to that of motorcycle, will be ?

(a) The same amount
(b) Twice as much.
(c) Three times as much
(d) Four times as much.

Question 39. Our planet Earth receives or transfers most of its energy in the form of :

(b) Geo-thermal energy
(c) Chemical energy
(d) Wind energy

Question 40. Two objects A and B are moving with same momentum. Mass of object 'B' is greater then mass of object 'A'. Which of the two object will have higher kinetic energy?

(a) Object A
(b) Object B
(c) Both the objects will have same Kinetic Energy
(d) Object with greater mass will have higher kinetic energy

Chapter 11 Work and Energy |CBSE Class 9th Science | Complete Solved Exercises

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