9th Class Science Work and energy Question Bank

done Work, Energy and Power Total Questions - 55

• question_answer1)
  Find the work done by a force of \[5\,\,N\] in displacing a book through \[20\,\,cm\] along the direction of the push.
  A)
  \[1J\]                               done clear
  B)
  \[3J\] done clear
  C)
  \[4J\]                 done clear
  D)
         \[5J\] done clear
  View Solution play_arrow

• question_answer2)
  A ball of mass \[1\,\,kg\] thrown upwards reaches a maximum height of\[5\,\,m\]. Calculate the work done by the force of gravity during this vertical displacement.
  A)
  \[-30\,\,J\]          done clear
  B)
         \[-48\,\,J\] done clear
  C)
  \[-49\,\,J\]            done clear
  D)
         \[-59\,\,J\] done clear
  View Solution play_arrow

• question_answer3)
  An object of mass \[1\,\,kg\] is raised through a height\['h'\]. Its potential energy is increased by\[1\,\,J\]. Find the height.
  A)
  \[0.102\,\,m\]       done clear
  B)
         \[0.105\,\,m\] done clear
  C)
  \[0.130\,\,m\]     done clear
  D)
         \[0.110\,\,m\] done clear
  View Solution play_arrow

• question_answer4)
  Find the kinetic energy of a ball of mass\[200\,\,g\] moving at a speed of\[20\,\,cm\,\,{{s}^{-1}}\].
  A)
  \[0.4\,\,J\]                      done clear
  B)
  \[0.004\,\,J\]   done clear
  C)
  \[0.001\,\,J\]       done clear
  D)
         \[0.01\,\,J\] done clear
  View Solution play_arrow

• question_answer5)
  Find the work done by a student in lifting a \[0.5\,\,kg\] book from the ground and keeping it on a shelf of height\[1.5\,\,m\]
  A)
  \[8.30\,\,J\]        done clear
  B)
         \[7.35\,\,J\]   done clear
  C)
  \[5.40\,\,J\]                    done clear
  D)
  \[0.1\,\,J\] done clear
  View Solution play_arrow

• question_answer6)
  A block of mass \[1\,\,kg\] slides down on an inclined plane with the angle of inclination of\[{{30}^{o}}\]. Find the work done as the block slides through\[50\,\,cm\].
  A)
  \[3.45\,\,J\]        done clear
  B)
         \[5.30\,\,J\] done clear
  C)
  \[2.45\,\,J\]          done clear
  D)
         \[4.50\,\,J\] done clear
  View Solution play_arrow

• question_answer7)
  A body of mass \[0.5\,\,kg\] is taken to a height \[{{R}_{e}}\]above the earth's surface, where \[{{R}_{e}}\] is the radius of the earth. If the body is now raised through a height of\[2\,\,m\], what is the increase in its potential energy?
  A)
  \[0.25\,\,J\]          done clear
  B)
         \[0.50\,\,J\] done clear
  C)
  \[0.75\,\,J\]        done clear
  D)
         \[1.25\,\,J\] done clear
  View Solution play_arrow

• question_answer8)
  A force of \[10\,\,N\] displaces an object through \[20\,\,cm\] and does the work of \[1\,\,J\] in the process. Find the angle between the force and displacement.
  A)
  \[\theta ={{60}^{o}}\]   done clear
  B)
         \[\theta ={{50}^{o}}\] done clear
  C)
  \[\theta ={{35}^{o}}\] done clear
  D)
         \[\theta ={{45}^{o}}\] done clear
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• question_answer9)
  How long will it take to perform \[440\,\,J\] of work at the rate of\[11\,\,W\]?
  A)
  \[50s\]               done clear
  B)
         \[40s\]   done clear
  C)
  \[30s\]               done clear
  D)
         \[20s\] done clear
  View Solution play_arrow

• question_answer10)
  When a stone tied to a string is whirled in a circle, what kind of work is said to be done on it by the string?
  A)
   Positive            done clear
  B)
          Negative done clear
  C)
   Zero                   done clear
  D)
          Undefined done clear
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• question_answer11)
  A man with a box on his head is climbing up a ladder. What work is said to be done by the man on the box?
  A)
   Positive              done clear
  B)
          Negative done clear
  C)
   Zero                 done clear
  D)
          Undefined done clear
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• question_answer12)
  A ball is thrown upwards from point\[A\]. It reaches up to point \[B\] and returns. What can be concluded?
  A)
   Kinetic energy at \[A=\] kinetic energy at \[B\] done clear
  B)
   Potential energy at \[A=\] potential energy at\[B\] done clear
  C)
   Potential energy at \[B=\] kinetic energy at\[B\] done clear
  D)
   Potential energy at \[B=\] kinetic energy at \[A\]   done clear
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• question_answer13)
  A does \[500\,\,J\] of work in \[10\] minutes and \[B\] does \[600\,\,J\] of work in \[20\] minutes. The power delivered by \[A\] and \[B\] is \[{{P}_{1}}\] and \[{{P}_{2}}\] respectively. Find the relation between\[{{P}_{1}}\]and\[{{P}_{2}}\].
  A)
  \[{{P}_{1}}={{P}_{2}}\] done clear
  B)
  \[{{P}_{1}}>{{P}_{2}}\]   done clear
  C)
  \[{{P}_{1}}<{{P}_{2}}\] done clear
  D)
  \[{{P}_{1}}\]and\[{{P}_{2}}\]are undefined done clear
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• question_answer14)
  The mass of a body is increased by \[100%\] and velocity of a body is decreased by\[50%\]. What is the percentage change in its kinetic energy?
  A)
  \[50%\]                          done clear
  B)
  \[-50%\]   done clear
  C)
  \[75%\]              done clear
  D)
         \[150%\] done clear
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• question_answer15)
  When the mass and velocity of the body are doubled/ what happens to its kinetic energy?
  A)
   It gets doubled. done clear
  B)
   It gets quadrupled. done clear
  C)
   It becomes eight times.   done clear
  D)
   It becomes one fourth. done clear
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• question_answer16)
  By how much does the kinetic energy of a particle increase if the velocity is increased by a factor of three?
  A)
  \[6\]                  done clear
  B)
         \[7\] done clear
  C)
  \[8\]                  done clear
  D)
         \[9\]   done clear
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• question_answer17)
  \[800\,\,g\] ball is pulled up a slope as shown in the figure. Calculate the potential energy it gains.
  A)
  \[1.96\,\,J\]        done clear
  B)
         \[1.57\,\,J\]   done clear
  C)
  \[7.84\,\,J\]        done clear
  D)
         \[1.26\,\,J\] done clear
  View Solution play_arrow

• question_answer18)
  The heart of a man pumps \[4\] litres of blood per minute at a pressure of \[130\,\,mm\] of mercury. If the density of mercury is\[13.6\,\,g\,\,c{{m}^{-3}}\], calculate the power of the heart.
  A)
  \[1.144\,\,W\]                 done clear
  B)
  \[2.145\,\,W\] done clear
  C)
  \[1.155\,\,W\]       done clear
  D)
         \[3.155\,\,W\] done clear
  View Solution play_arrow

• question_answer19)
  A body falling from a height of \[10\,\,m\] rebounds from a hard floor. It loses \[20%\] of its energy in the impact. What could be the height to which it would rise after the impact?
  A)
  \[7\,\,m\]                                    done clear
  B)
  \[5\,\,m\] done clear
  C)
  \[8\,\,m\]                          done clear
  D)
         \[6\,\,m\] done clear
  View Solution play_arrow

• question_answer20)
  A force of \[5\,\,N\] acts on an object. The displacement is perpendicular to the direction of the force. What is the work done?
  A)
  \[5J\]                 done clear
  B)
         \[1J\] done clear
  C)
  \[100J\] done clear
  D)
         \[0J\]   done clear
  View Solution play_arrow

• question_answer21)
  The kinetic energy of a body is increased by\[21%\]. What is the percentage increase in the linear momentum of the body?
  A)
  \[20%\]              done clear
  B)
         \[10%\]   done clear
  C)
  \[30%\]              done clear
  D)
         \[5%\] done clear
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• question_answer22)
  A lorry and a car with the same kinetic energy are brought to rest by the application of brakes which provide equal retarding forces. Which of them will come to rest in a shorter distance?
  A)
   Lorry done clear
  B)
   Car done clear
  C)
   Both will stop at the same distance   done clear
  D)
   Car stops first but takes longer distance. done clear
  View Solution play_arrow

• question_answer23)
  What should be the angle between the force and displacement for maximum work?
  A)
  \[{{0}^{o}}\]                 done clear
  B)
         \[{{30}^{o}}\] done clear
  C)
  \[{{60}^{o}}\]             done clear
  D)
         \[{{90}^{o}}\] done clear
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• question_answer24)
  A block of wood of mass \[250\,\,g\] is moving at a speed of\[4\,\,m\,\,{{s}^{-1}}\]. Find its \[K.E.\] in Joules.
  A)
  \[4J\]                 done clear
  B)
         \[2J\]   done clear
  C)
  \[1J\]                 done clear
  D)
         \[10J\] done clear
  View Solution play_arrow

• question_answer25)
  If \[P.E.\] of the body and the height through which it falls freely are plotted on a graph, it may be noted that the total energy remains the same. Which of the following graphs shows this relation correctly?
  A)
    done clear
  B)
         done clear
  C)
  done clear
  D)
         done clear
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• question_answer26)
  A block of mass \[20\,\,kg\] is pulled over a smooth inclined plane through \[3\,\,m\] as shown in the figure. The plane makes an angle of \[{{30}^{o}}\] with the base. The force applied is parallel to the base.\[(g=10\,\,m\,\,{{s}^{-2}})\] Assuming that no energy is lost otherwise, what is the gain in the P.E. of the block?
  A)
  \[30J\]               done clear
  B)
         \[20J\] done clear
  C)
  \[300J\]   done clear
  D)
         \[600J\] done clear
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• question_answer27)
  The rectangular components of a force are applied to move a body. One of the components is\[30\,\,N\]. What should be the other component to obtain a resultant force of\[50\,\,N\]?
  A)
  \[30\,\,N\]          done clear
  B)
         \[40\,\,N\]   done clear
  C)
  \[50\,\,N\]          done clear
  D)
         \[90\,\,N\] done clear
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• question_answer28)
  A stone is thrown vertically up. What happens to its RE. during its motion of upward journey ?
  A)
   Decreases till it becomes minimum done clear
  B)
   Increases till it becomes maximum   done clear
  C)
   First decreases and then increases done clear
  D)
   First increases and then decreases done clear
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• question_answer29)
  Water is falling at the rate of \[1000\,\,kg\] per second. The height of the fall is about\[100\,\,m\]. The potential energy of water when it falls on the blades will be conveyed to them and \[P.E.\] is converted into \[K.E.\] of blades. Estimate the power that could be generated, if energy is not lost otherwise (Take the value of gas\[10\,\,m{{s}^{-2}}\]).
  A)
  \[10\,\,W\]          done clear
  B)
         \[100\,\,W\] done clear
  C)
  \[{{10}^{6}}W\]            done clear
  D)
         \[{{10}^{5}}W\] done clear
  View Solution play_arrow

• question_answer30)
  What energy does the person possess while climbing a hill?
  A)
   Only\[P.E.\] done clear
  B)
   Only\[K.E.\] done clear
  C)
   Only muscular energy done clear
  D)
   Both [a] and [b]   done clear
  View Solution play_arrow

• question_answer31)
  A gun fires a bullet of mass \[m\] with velocity\[v\]. The mass of the gun is \[M\] and it recoils with velocity\[V\]. If the kinetic energy of the bullet is \[{{E}_{b}}\] and that of the gun is\[{{E}_{g'}}\] identify the relation between\[{{E}_{b}}\]and\[{{E}_{g'}}\].
  A)
  \[{{E}_{b}}={{E}_{g}}\]          done clear
  B)
         \[{{E}_{b}}<{{E}_{g}}\] done clear
  C)
  \[{{E}_{b}}>{{E}_{g}}\]            done clear
  D)
         \[{{E}_{b}}\ge {{E}_{g}}\] done clear
  View Solution play_arrow

• question_answer32)
  Which of the following is NOT a measure of energy?
  A)
  \[J\,\,s\]               done clear
  B)
         \[W\,\,s\] done clear
  C)
  \[kWh\]              done clear
  D)
         \[erg\] done clear
  View Solution play_arrow

• question_answer33)
  Find the power of a pump which takes \[10\,\,s\] to draw \[100\,\,kg\] of water from a tank situated at a height of\[20\,\,m\].
  A)
  \[2\times {{10}^{4}}W\]           done clear
  B)
         \[2\times {{10}^{3}}W\]   done clear
  C)
  \[200\,\,W\]        done clear
  D)
         \[1\,\,kW\] done clear
  View Solution play_arrow

• question_answer34)
  Calculate the kinetic energy of a body of mass \[10\,\,kg\] moving with a velocity\[2\,\,m\,\,{{s}^{-1}}\].
  A)
  \[40\,\,J\]                                   done clear
  B)
  \[20\,\,J\]   done clear
  C)
  \[30\,\,J\]                       done clear
  D)
         \[10\,\,J\] done clear
  View Solution play_arrow

• question_answer35)
  A girl of mass \[40\,\,kg\] climbs \[50\] stairs each of average height \[20\,\,cm\] in\[50\,\,s\]. Find the power of the girl\[(g=10\,\,m\,\,{{s}^{-2}})\]
  A)
  \[50\,\,W\]                      done clear
  B)
  \[50\times 20\,\,W\] done clear
  C)
  \[80\,\,W\]            done clear
  D)
         \[50\times 20\times 2\,\,W\] done clear
  View Solution play_arrow

• question_answer36)
  In which of the following cases is the work done the maximum?
  A)
         done clear
  B)
         done clear
  C)
           done clear
  D)
         done clear
  View Solution play_arrow

• question_answer37)
  An engine can pump \[40,000\] litres of water to a vertical height of \[35\] metres in \[5\] minutes. Calculate the gravitational potential energy of water at the given height.
  A)
  \[39.2\times {{10}^{4}}J\]        done clear
  B)
         \[1.4\times {{10}^{6}}J\] done clear
  C)
  \[1.37\times {{10}^{7}}J\]          done clear
  D)
         \[8.5\times {{10}^{-3}}J\] done clear
  View Solution play_arrow

• question_answer38)
  In which of the following applications is work NOT done?
  A)
   Shopping in the supermarket done clear
  B)
   Standing with a basket of fruits on the head   done clear
  C)
   Climbing a tree to pluck fruits done clear
  D)
   Pushing a wheelbarrow of bricks done clear
  View Solution play_arrow

• question_answer39)
  A boy lifts a book of known weight from the surface of a table. To calculate the work done, what does he need to know?
  A)
   The mass of the book done clear
  B)
   The height   done clear
  C)
   The cost of the book done clear
  D)
   The time taken by him done clear
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• question_answer40)
  Two bodies of unequal masses possess the same momentum. Which of the following can be concluded?
  A)
   Heavier mass possesses lesser\[K.E.\]   done clear
  B)
   The masses of the two bodies are in the direct ratio of their velocities. done clear
  C)
   Lighter mass possesses less\[K.E.\] done clear
  D)
   Both [a] and [b] done clear
  View Solution play_arrow

• question_answer41)
  A \[20\,\,kg\] ball is thrown upwards with a speed of\[6\,\,m\,\,{{s}^{-1}}\]. Find the maximum height it reaches\[(g=9.8\,\,m\,\,{{s}^{-2}})\].
  A)
  \[2.86\,\,m\]       done clear
  B)
         \[1.88\,\,m\] done clear
  C)
  \[3.82\,\,m\]       done clear
  D)
         \[1.84\,\,m\]   done clear
  View Solution play_arrow

• question_answer42)
  In a factory, due to a sudden strike the work usually done in a day took a longer time. Which of the following happened?
  A)
   Power increased. done clear
  B)
   Power decreased.   done clear
  C)
   Energy increased. done clear
  D)
   Energy decreased. done clear
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• question_answer43)
  A boy moved a body through 3 m in four different ways. In which of the following cases was the work done the maximum?
  A)
   Pushing a body over an inclined plane done clear
  B)
   Lifting a body vertically upwards   done clear
  C)
   Pushing a body over smooth rollers done clear
  D)
   Pushing on a plane horizontal surface done clear
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• question_answer44)
  Work is said to be NOT done when an object moves
  A)
   at an angle of \[{{90}^{o}}\] to the direction of the force.   done clear
  B)
   at an angle opposite to the direction of the force. done clear
  C)
   at any angle to the direction of the force. done clear
  D)
   along the direction of the force. done clear
  View Solution play_arrow

• question_answer45)
  Two bodies of masses \['m'\] and \['2m'\] are thrown upwards with a velocity of \['u'\] and \['3u'\] from the surface respectively. What is the ratio of their potential energies at the highest point?
  A)
  \[1:9\]                  done clear
  B)
         \[3:1\] done clear
  C)
  \[3:2\]                done clear
  D)
         \[4:1\] done clear
  View Solution play_arrow

• question_answer46)
  An engine of \[4.9\,\,kW\] power is used to pump water from a well which is \[20\,\,m\] deep. What quantity of water in kilolitres can it pump out in\[30\] minutes?
  A)
  \[45\,\,kl\]            done clear
  B)
         \[75\,\,kl\] done clear
  C)
  \[25\,\,kl\]          done clear
  D)
         \[90\,\,kl\] done clear
  View Solution play_arrow

• question_answer47)
  A ball dropped from a \[20\,\,m\] height loses \[40%\] of its energy on hitting the ground. Up to what height does the ball rebound?
  A)
  \[28\,\,m\]         done clear
  B)
         \[8\,\,m\] done clear
  C)
  \[12\,\,m\]           done clear
  D)
         \[20\,\,m\] done clear
  View Solution play_arrow

• question_answer48)
  The work done by a man in holding a \[15\,\,kg\] suitcase while waiting for a bus for \[45\] minutes is
  A)
  \[675\,\,J\]         done clear
  B)
         \[405\,\,J\] done clear
  C)
  \[450\,\,J\]         done clear
  D)
         \[zero\]   done clear
  View Solution play_arrow

• question_answer49)
  Three different stones \[P,\,\,Q\] and \[R\] of different weights are lifted from the ground level to different heights on different planets as given below:

  P: A 250 g stone is lifted to 10 m on the Earth.

  Q: A 800 g stone is lifted to 2 m on Saturn.

  R: A 1kg stone is lifted to 1 m on Jupiter.

  Which of the following statements is true? (Given that the acceleration due to gravity on the Earth, the Saturn and the Jupiter are \[10\,\,m\,\,{{s}^{-2}},\,\,15\,\,m\,\,{{s}^{-2}}\] and \[25\,\,m\,\,{{s}^{-2}}\] respectively).
  A)
   More energy is required to lift stone \[Q\] than stone\[P\]. done clear
  B)
   More energy is required to lift stone \[P\] than stone\[R\]. done clear
  C)
   Stone \[P\] and stone \[Q\] require the same amount of energy. done clear
  D)
   Stone \[P\] and stone \[R\] require the same amount of energy.   done clear
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• question_answer50)
  A ball is projected upwards. As it rises, there is an increase in its
  A)
   momentum    done clear
  B)
          retardation done clear
  C)
   kinetic energy    done clear
  D)
   potential energy   done clear
  View Solution play_arrow

• question_answer51)
  A ball of mass \[2\,\,kg\] and another of mass \[4\,\,kg\] are dropped together from a \[60\] feet tall building. What will be the ratio of their kinetic energies after a fall of \[30\] feet?
  A)
  \[\sqrt{2}:1\]      done clear
  B)
         \[1:4\] done clear
  C)
  \[1:2\]                  done clear
  D)
         \[1:\sqrt{2}\] done clear
  View Solution play_arrow

• question_answer52)
  Rahul takes \[1\] minute to raise a box to a height of 1 metre and Rohan takes \[1/2\] minute to do the same. Which of the following is true of the energy spent by the two?
  A)
   Energy spent by Rahul is more. done clear
  B)
   Energy spent by both Rahul and Rohan is the same.   done clear
  C)
   Energy spent by Rohan is more. done clear
  D)
   Energy spent by Rahul is less. done clear
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• question_answer53)
  When a force retards the motion of a body, the work done by the force during retardation is
  A)
   zero done clear
  B)
   negative   done clear
  C)
   positive done clear
  D)
   positive or negative depending upon the magnitude of force. done clear
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• question_answer54)
  Analyse the given statements and choose the correct option. Statement I: The kinetic energy, with any reference, must be positive. Statement II: The kinetic energy and the square velocity are related.
  A)
   Both statement I and statement II are correct and statement II is the correct explanation of statement I.   done clear
  B)
   Both statement I and statement II are correct, but statement II is not the correct explanation of statement I. done clear
  C)
   Statement I is correct, but statement II is incorrect. done clear
  D)
   Statement I is incorrect, but statement II is correct. done clear
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• question_answer55)
  Rakesh lifts a heavy book from the floor of the room and puts it in the book shelf of height\[2\,\,m\]. In this process, he takes \[5\] seconds. On which of the following does the work done by him depend?
  A)
   Mass of the book and the time taken to do work done clear
  B)
   Weight of the book and the height of the book shelf   done clear
  C)
   Height of the book shelf and the time taken to do work done clear
  D)
   Mass of the book, height of the book shelf and the time taken to do work done clear
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