9th Class Science Work and energy Question Bank

done Work, Energy and Power Total Questions - 89

• question_answer1)
  When a light and a heavy body have equal K.E, then which one has a greater momentum?
  A)
   light body done clear
  B)
   heavy body   done clear
  C)
   both have equal momentum done clear
  D)
   uncertain done clear
  View Solution play_arrow

• question_answer2)
  In SI system, the unit of P.E. is
  A)
   erg                        done clear
  B)
          dyne-cm done clear
  C)
   \[J\]                        done clear
  D)
          none of these done clear
  View Solution play_arrow

• question_answer3)
  Kilowatt hour (\[\text{kWh}\]) represents the unit of
  A)
   power            done clear
  B)
          impulse done clear
  C)
   momentum      done clear
  D)
          none of these   done clear
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• question_answer4)
  When speed of a motor car increases six times, then kinetic energy increases by
  A)
   6 times          done clear
  B)
          36 times   done clear
  C)
   12 times         done clear
  D)
          24 times done clear
  View Solution play_arrow

• question_answer5)
  1 kWh equals
  A)
  \[\text{36 }\times \text{ 1}{{0}^{\text{2}}}\text{ Joules}\] done clear
  B)
          \[\text{36 }\times \text{ 1}{{0}^{\text{4}}}\text{ Joules}\] done clear
  C)
  \[\text{3}.\text{6 }\times \text{ 1}{{0}^{\text{6}}}\text{ Joules}\]   done clear
  D)
          none of these done clear
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• question_answer6)
  When speed of the moving object is doubled its
  A)
   acceleration is doubled done clear
  B)
   momentum becomes four times more done clear
  C)
   K. E. is increased to four times   done clear
  D)
   potential energy is increased done clear
  View Solution play_arrow

• question_answer7)
  When time taken to complete a given amount of work increases, then
  A)
   power increases done clear
  B)
          power decreases   done clear
  C)
   energy increases done clear
  D)
         energy decreases done clear
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• question_answer8)
  When the force applied and the displacement of the body are inclined at \[30{}^\circ \] with each other, then work done is
  A)
   infinite           done clear
  B)
          maximum done clear
  C)
   zero                        done clear
  D)
          unity done clear
  View Solution play_arrow

• question_answer9)
  The K.E. of a body in increased most by doubling its
  A)
   mass                     done clear
  B)
          weight done clear
  C)
   speed               done clear
  D)
          density done clear
  View Solution play_arrow

• question_answer10)
  The energy required to raise a given volume of water from a well can be
  A)
   mega watts       done clear
  B)
          mega newton done clear
  C)
   mega joules        done clear
  D)
          kilowatts done clear
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• question_answer11)
  The slope of kinetic-energy-displacement curve of a particle in motion is
  A)
   equal to the acceleration of the particle done clear
  B)
   inversely proportional to the acceleration done clear
  C)
   directly proportional to the acceleration   done clear
  D)
   none of these done clear
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• question_answer12)
  If a force F is applied on a body and it moves with velocity v, then power will be
  A)
   \[F\times \upsilon \]                       done clear
  B)
   \[\frac{F}{{{\upsilon }^{2}}}\] done clear
  C)
   \[\frac{F}{\upsilon }\]                   done clear
  D)
          \[F\times {{v}^{2}}\] done clear
  View Solution play_arrow

• question_answer13)
  The displacement \[x\] of a particle moving in one dimension, under the action of a constant force, is related to the time t by the equation,\[t=\sqrt{x}+3\]where \[x\] is in metres and t in seconds. The displacement of the particle when its velocity is zero, is
  A)
   0                               done clear
  B)
          6 m done clear
  C)
   12m                      done clear
  D)
          18m done clear
  View Solution play_arrow

• question_answer14)
  The relationship between force and position is shown in the figure (in One dimensional case). Work done by the force is displacing a body from \[x\] = 1 cm to \[x\] = 5 cm is
  A)
   700 ergs done clear
  B)
   70 ergs done clear
  C)
   60 ergs done clear
  D)
   20 ergs   done clear
  View Solution play_arrow

• question_answer15)
  Work done by a centripetal force
  A)
   increases by decreasing the radius of the circle done clear
  B)
   decreases by increasing the radius of the circle done clear
  C)
   increases by increasing the mass of the body done clear
  D)
   is always zero   done clear
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• question_answer16)
  A 1 kg mass falls from a height of 10 m into a sand box. What is the speed of the mass just before hitting the sand box? If it travels a distance of 2 cm into the sand before coming to rest, what is the average retarding force?
  A)
   12 m/sec and 3600N done clear
  B)
   14 m/sec and 4900N   done clear
  C)
   16 m/sec and 6400N done clear
  D)
   18 m/sec and 8100N done clear
  View Solution play_arrow

• question_answer17)
  Work done in moving a 50 kg block through a horizontal distance of 10 m by applying a force of 100N which makes an angle of \[60{}^\circ \] with the horizontal is
  A)
   200 joules        done clear
  B)
          425 joules done clear
  C)
   500 joules           done clear
  D)
          575 joules done clear
  View Solution play_arrow

• question_answer18)
  A particle of mass 4 m which is at rest and explodes into three fragments. Two of the fragments each of mass \[m\] are found to move with a speed \[\upsilon \] in mutually perpendicular directions. The total energy released in the explosion is
  A)
  \[\text{2m}{{\upsilon }^{\text{2}}}\]                      done clear
  B)
          \[\frac{1}{2}\text{ m}{{\upsilon }^{\text{2}}}\] done clear
  C)
  \[\text{m}{{\upsilon }^{\text{2}}}\]                         done clear
  D)
          \[\frac{3}{2}\text{m}{{\upsilon }^{\text{2}}}\]   done clear
  View Solution play_arrow

• question_answer19)
  \[kWh\] is the unit of
  A)
   force                    done clear
  B)
          power done clear
  C)
   time                                      done clear
  D)
   energy   done clear
  View Solution play_arrow

• question_answer20)
  A man throws the bricks to the height of 12 m where they reach with a speed of 12 m/s. If he throws the bricks such that they just reach this height, then what percentage of energy will he save?
  A)
   19%                       done clear
  B)
          38%   done clear
  C)
   57%                       done clear
  D)
          76% done clear
  View Solution play_arrow

• question_answer21)
  The potential energy of a certain spring when stretched through a distance 'S' is 10 joules. The amount of work (in joule) that must be done on this spring to stretch it through an additional distance "S" will be
  A)
   30                            done clear
  B)
          40 done clear
  C)
   10                          done clear
  D)
          20 done clear
  View Solution play_arrow

• question_answer22)
  Two bodies with masses \[{{M}_{A}}\] and \[{{M}_{B}}\] are moving with equal kinetic energy. Their linear momenta are numerically in a ratio \[\left| {{P}_{A}} \right|:\left| {{P}_{B}} \right|\], will be
  A)
  \[{{M}_{B}}:{{M}_{A}}\]                done clear
  B)
          \[{{M}_{A}}:{{M}_{B}}\] done clear
  C)
   \[\sqrt{{{M}_{A}}}:\sqrt{{{M}_{B}}}\]   done clear
  D)
          \[{{M}_{A}}^{2}:{{M}_{B}}^{2}\] done clear
  View Solution play_arrow

• question_answer23)
  A ball is allowed to fall from a height of 10 there is 40% loss of energy due to impact, after one impact ball will go upto
  A)
   10 m               done clear
  B)
          8 m               done clear
  C)
   4m                  done clear
  D)
          6m   done clear
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• question_answer24)
  Mechanical work done is equal to (symbols have their usual meanings)
  A)
   \[W=\frac{F}{S}\]            done clear
  B)
          \[W=FS\]   done clear
  C)
   \[W=F+S\]         done clear
  D)
          \[W=F-S\] done clear
  View Solution play_arrow

• question_answer25)
  A body at rest can have
  A)
   speed done clear
  B)
   energy   done clear
  C)
   momentum done clear
  D)
   velocity done clear
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• question_answer26)
  An elevator is designed to lift a load of 1000 kg, through 6 floors of a building averaging \[\text{3}\text{.5 m}\]per floor in 6 sec. Power of the elevator, neglecting other losses, will be
  A)
  \[\text{3}\text{.43 }\times \text{ 1}{{0}^{\text{4}}}\text{ watt}\]   done clear
  B)
          \[\text{4}\text{.33 }\times \text{ 1}{{0}^{\text{4}}}\text{ watt}\] done clear
  C)
  \[\text{2}\text{.21 }\times \text{ 1}{{0}^{\text{4}}}\text{ watt}\] done clear
  D)
          \[\text{5}\text{.65 }\times \text{ 1}{{0}^{\text{4}}}\text{ watt}\] done clear
  View Solution play_arrow

• question_answer27)
  A car of mass 2000 kg is to be stopped from a speed of 72 km/hr. If the coefficient of friction between tyres and road is 0.4, then distance travelled before coming to rest is \[\left( \text{g }=\text{ 1}0\text{ m}/{{\text{s}}^{\text{2}}} \right)\]
  A)
   25 m                                     done clear
  B)
   50 m   done clear
  C)
   75 m                                     done clear
  D)
   100 m done clear
  View Solution play_arrow

• question_answer28)
  Which of the following physical quantity is different from others?
  A)
   Work done clear
  B)
   Kinetic energy done clear
  C)
   Force   done clear
  D)
   Potential energy done clear
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• question_answer29)
  When a body is whirled in a circle, then work done on it is
  A)
   positive done clear
  B)
   negative done clear
  C)
   zero   done clear
  D)
   infinite done clear
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• question_answer30)
  A tennis ball dropped from a height of 2 m rebounds only 1.5 m after hitting the ground. What fraction of energy is lost in the impact?
  A)
   \[\frac{1}{4}\]                       done clear
  B)
          \[\frac{1}{8}\] done clear
  C)
   \[\frac{1}{2}\]                    done clear
  D)
          \[\frac{1}{16}\] done clear
  View Solution play_arrow

• question_answer31)
  A crane is used to lift 1000 kg of coal from a mine 100 m deep. If the time taken by the crane is 1 hr then find the power of the crane, assuming the efficiency of the crane to be 80%. \[\left( \text{g }=\text{9}.\text{8 m}/{{\text{s}}^{\text{2}}} \right)\]
  A)
   2567 watts done clear
  B)
   2403 watts done clear
  C)
   3403 watts   done clear
  D)
   3761 watts done clear
  View Solution play_arrow

• question_answer32)
  A uniform chain of length L and mass M is lying on a smooth table and one-third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, then work required to pull the hanging part on to the table is
  A)
   \[MgL\]               done clear
  B)
          \[\frac{MgL}{3}\] done clear
  C)
   \[\frac{MgL}{9}\]            done clear
  D)
          \[\frac{MgL}{18}\]   done clear
  View Solution play_arrow

• question_answer33)
  Unit of power is
  A)
   watt per second done clear
  B)
          joule done clear
  C)
   watt                                        done clear
  D)
   none of these done clear
  View Solution play_arrow

• question_answer34)
  The mass of an object P is double the mass of object \[Q\]. If both move with the same velocity, then ratio of K.E. of \[P\] to \[Q\] is
  A)
   1: 2                        done clear
  B)
          2 : 1   done clear
  C)
   1 : 4                  done clear
  D)
          4 : 1 done clear
  View Solution play_arrow

• question_answer35)
  1 hp is equal to
  A)
   0.746 kW               done clear
  B)
   7.46 kW done clear
  C)
   74.6 kW           done clear
  D)
          746 kW done clear
  View Solution play_arrow

• question_answer36)
  A truck can move up a road having the grade of 1 m rise for every 50 m with a speed of 15 km/hr. The resisting force is equal to \[\frac{1}{25}\] th the weight Au of the truck. How fast will the same truck move down the hill with the same horse power?
  A)
   30 km/hr             done clear
  B)
   45 km/hr   done clear
  C)
   60km7hr        done clear
  D)
          75 km/hr done clear
  View Solution play_arrow

• question_answer37)
  A bullet is fired at a target with a velocity 80 m/s and penetrates 50 cm into it. If this bullet were fired into a target 25 cm thick with equal velocity, with what velocity would it emerge, supposing the resistance to be uniform and the same in both the cases?
  A)
   \[\sqrt{80}m/s\]              done clear
  B)
          \[\frac{40}{\sqrt{2}}m/s\] done clear
  C)
   \[40m/s\]           done clear
  D)
          \[40\sqrt{2}m/s\]   done clear
  View Solution play_arrow

• question_answer38)
  A body of mass 1 kg strikes elastically with another body at rest and continues to move in the same direction with one fourth the initial velocity. The mass of the other body is
  A)
   3 kg            done clear
  B)
                         0.6kg   done clear
  C)
   2.4kg                    done clear
  D)
          4kg done clear
  View Solution play_arrow

• question_answer39)
  A body rolling down a hill has
  A)
   K.E. only done clear
  B)
   RE. only done clear
  C)
   neither K.E. nor RE. done clear
  D)
   both [a] and [b]   done clear
  View Solution play_arrow

• question_answer40)
  A stretched spring possesses
  A)
   kinetic energy done clear
  B)
   elastic potential energy   done clear
  C)
   electric energy done clear
  D)
   magnetic energy done clear
  View Solution play_arrow

• question_answer41)
  If L, M denote the angular momentum and mass of a particle and p its linear momentum. Which of the following can represent the kinetic energy of the particle moving in a circle of radius R?
  A)
   \[\frac{{{L}^{2}}}{2M}\]                done clear
  B)
          \[\frac{{{P}^{2}}}{M}\] done clear
  C)
   \[\frac{{{L}^{2}}}{2M{{R}^{2}}}\]                done clear
  D)
          \[\frac{1}{2}Mp\] done clear
  View Solution play_arrow

• question_answer42)
  A body is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to
  A)
   \[{{t}^{\frac{3}{2}}}\]                      done clear
  B)
          \[{{t}^{\frac{1}{2}}}\] done clear
  C)
   \[{{t}^{\frac{3}{4}}}\]                    done clear
  D)
          \[{{t}^{2}}\] done clear
  View Solution play_arrow

• question_answer43)
  A machine, which is 75 percent efficient uses 12 joules of energy in lifting up a 1 kg mass through a certain distance. The mass is then allowed to fall through that distance. What will its velocity be at the end of its fall?
  A)
   \[\sqrt{\text{32}}\text{ m}/\text{s}\] done clear
  B)
   \[\sqrt{\text{24}}\text{ m}/\text{s}\] done clear
  C)
   \[\sqrt{\text{l8}}\text{ m}/\text{s}\]   done clear
  D)
   \[\sqrt{\text{9}}\text{ m}/\text{s}\] done clear
  View Solution play_arrow

• question_answer44)
  When a person climbs a hill, he possesses
  A)
   only K.E. done clear
  B)
   only RE. done clear
  C)
   both K.E. and RE.   done clear
  D)
   none of these done clear
  View Solution play_arrow

• question_answer45)
  A particle of mass m moves in a circular orbit of radius r under in action of an attractive force \[\frac{-{{K}^{2}}}{{{r}^{2}}}\] which always acts towards the centre r of the orbit. What is the total energy in the particle?
  A)
   \[\frac{k}{{{r}^{2}}}\]                    done clear
  B)
          \[\frac{2k}{r}\] done clear
  C)
   \[\frac{{{k}^{2}}}{r}\]                    done clear
  D)
          \[\frac{k}{2r}\]   done clear
  View Solution play_arrow

• question_answer46)
  Which of the following graphs closely represents the kinetic energy (K) of a freely falling body and its height (h) above the ground?
  A)
    done clear
  B)
  done clear
  C)
  done clear
  D)
  done clear
  View Solution play_arrow

• question_answer47)
  A stone of mass m kg is whirled in a vertical circle of radius 20 cm. The difference in the kinetic energies at the lowest and the topmost positions is
  A)
   4 mg joules       done clear
  B)
          0.4 mg joules   done clear
  C)
   40 mg joules      done clear
  D)
          None of these done clear
  View Solution play_arrow

• question_answer48)
  The bag of sand of mass 2 kg is suspended by a rope. A bullet of mass 10 g is fired at it and gets embedded into it. The bag rises up a vertical height of 10 cm. The initial velocity of the bullet is nearly
  A)
   70 m/s            done clear
  B)
          140 m/s done clear
  C)
   210 m/s           done clear
  D)
          280 m/s   done clear
  View Solution play_arrow

• question_answer49)
  Which of the following graphs closely represents the P.E (U) of a freely falling body and its height (h) above the ground?
  A)
    done clear
  B)
  done clear
  C)
  done clear
  D)
  done clear
  View Solution play_arrow

• question_answer50)
  A rope ladder with a length 1 carrying a man with  a mass m at its end is attached to the basket of balloon with a mass M. The entire system if equilibrium in the air. As the man climbs up the ladder into the balloon, the balloon descend by  a height h. Then the potential energy of the man
  A)
   increases by \[mg\]\[\left( \text{1}-\text{h} \right)\]           done clear
  B)
   increases b \[mgl\]                        done clear
  C)
   increases by \[mgh\] done clear
  D)
   increases by mg                                                                                                                    \[(2l-h)\] done clear
  View Solution play_arrow

• question_answer51)
  In question No. 50, the potential energy of the balloon
  A)
   decreases by \[mgh\] done clear
  B)
   increases by \[mgh\]   done clear
  C)
   increases by \[mg(1-h)\] done clear
  D)
   increases by \[mgl\] done clear
  View Solution play_arrow

• question_answer52)
  In question No. 50, the work down by the man is
  A)
   \[mgl\]                  done clear
  B)
          \[mgh\] done clear
  C)
   \[\frac{1}{2}mgl\]           done clear
  D)
          \[mg(1-h)\] done clear
  View Solution play_arrow

• question_answer53)
  The heart of a man pumps 4000 c.c. of blood through the arteries/per minute at a pressure of 130 mm Hg. If the density of mercury is\[13.6\times {{10}^{3}}\,kg/{{m}^{3}}\], what is the power of heart?
  A)
   \[1.15\] watt                       done clear
  B)
   \[2.30\]watt done clear
  C)
   \[1.15\] H.P          done clear
  D)
          \[0.115\] H.P done clear
  View Solution play_arrow

• question_answer54)
  Once a choice made regarding zero potential energy reference state, the changes in potential energy
  A)
   are same   done clear
  B)
   are different done clear
  C)
   depend strictly on the choice of the zero potential                   done clear
  D)
   become in determine                   done clear
  View Solution play_arrow

• question_answer55)
  Two spheres of the same diameter, one of mass 5 kg and the other of 1 kg are dropped at the same time from the top of a tower. When they are 1 metre above the ground the two sphere have the same                          
  A)
   momentum                       done clear
  B)
   kinetic energy done clear
  C)
   potential energy             done clear
  D)
   acceleration   done clear
  View Solution play_arrow

• question_answer56)
  It is easier to draw a Wooden block along an inclined plane than to rise it vertically, because
  A)
   friction decreased done clear
  B)
   only part of the weight is to be overcome   done clear
  C)
   g is decreased done clear
  D)
   none of the above done clear
  View Solution play_arrow

• question_answer57)
  A bag P (mass M) hangs by a long thread and a bullet (mass m) comes horizontally with velocity v and gets caught in the bag. Then for the combined (bag + bullet) system
  A)
   momentum is \[\frac{m\upsilon M}{M+m}\] done clear
  B)
   kinetic energy is \[\frac{m{{V}^{2}}}{2}\] done clear
  C)
   momentum is \[\frac{m\upsilon (M+m)}{M}\] done clear
  D)
   kinetic energy is \[\frac{{{m}^{2}}{{v}^{2}}}{2(M+m)}\]   done clear
  View Solution play_arrow

• question_answer58)
  The work down in time t on a body of mass m which is accelerated from rest to a speed \[{{v}_{1}}\] in time \[{{t}_{1}}\] as a function of time t is given by
  A)
   \[\frac{1}{2}m\frac{{{\upsilon }_{1}}}{{{t}_{1}}}{{t}^{2}}\]            done clear
  B)
          \[m\frac{{{\upsilon }_{1}}}{{{t}_{1}}}{{t}^{2}}\] done clear
  C)
   \[\frac{1}{2}{{\left( \frac{m{{\upsilon }_{1}}}{{{t}_{1}}} \right)}^{2}}{{t}^{2}}\]    done clear
  D)
          \[\frac{1}{2}m{{\frac{{{\upsilon }_{1}}}{{{t}_{1}}}}^{2}}{{t}^{2}}\]   done clear
  View Solution play_arrow

• question_answer59)
  A neutron travelling with a velocity v and kinetic energy E collides perfectly elastically head on with the nucleus of an atom of mass number A at rest. The fraction of total energy retained by the neutron is
  A)
   \[{{\left( \frac{A-1}{A+1} \right)}^{2}}\]                  done clear
  B)
          \[{{\left( \frac{A+1}{A-1} \right)}^{2}}\] done clear
  C)
   \[{{\left( \frac{A-1}{A} \right)}^{2}}\]     done clear
  D)
          \[{{\left( \frac{A+1}{A} \right)}^{2}}\] done clear
  View Solution play_arrow

• question_answer60)
  A moving body with a mass \[{{m}_{2}}\]\[{{m}_{1}}\] strike a stationary body of mass \[{{m}_{2}}\]. The masses  \[{{m}_{2}}\]and \[{{m}_{2}}\] should be in the ratio \[\frac{{{m}_{1}}}{{{m}_{2}}}\] so as to decrease the velocity of the first body \[1.5\] times assuming a perfectly elastic impact. Then the ratio \[\frac{{{m}_{1}}}{{{m}_{2}}}\] is
  A)
   \[\frac{1}{25}\]               done clear
  B)
          \[\frac{1}{5}\] done clear
  C)
   5                               done clear
  D)
          25 done clear
  View Solution play_arrow

• question_answer61)
  A particle moving along a line travels a distance of 10 m under the action of a force of 5 N. If the work done is 25 J, then the angle between the force and the direction of motion is
  A)
  \[0{}^\circ \]                       done clear
  B)
         \[30{}^\circ \] done clear
  C)
  \[45{}^\circ \] done clear
  D)
         \[60{}^\circ \]   done clear
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• question_answer62)
  A metre rod of mass 1-2 kg is pivoted at one end and hangs vertically. It is displaced through an angle of \[60{}^\circ \]. The increase in potential energy is........ Given : \[g=10\,m{{s}^{-2}}\]
  A)
   1 Joule            done clear
  B)
          \[1.5\] Joule done clear
  C)
   3 Joule              done clear
  D)
          6 Joule done clear
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• question_answer63)
  A motor of power P is employed to deliver water at a certain rate from a given pipe. In order to obtain thrice as much water from the same pipe in the same time, another motor of power P' is required. Given:\[\text{g}=\text{9}.\text{3489 m}{{\text{s}}^{\text{-2}}}\]Now, the ratio \[P'/P\] equals
  A)
   27                            done clear
  B)
          81 done clear
  C)
   561                        done clear
  D)
          \[{{\left( \text{9}.\text{3489} \right)}^{\text{3}}}\] done clear
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• question_answer64)
  The angle between the applied force and the momentum at time is
  A)
  \[0{}^\circ \]                       done clear
  B)
         \[30{}^\circ \] done clear
  C)
  \[60{}^\circ \] done clear
  D)
         \[90{}^\circ \]   done clear
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• question_answer65)
  A 500 gm ball is thrown vertically upwards with a kinetic energy 58.8 J. The kinetic energy is reduced to half at a height of.......... metre above the point of throw,
  A)
   2m                  done clear
  B)
          3 m done clear
  C)
   5m                         done clear
  D)
          6 m   done clear
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• question_answer66)
  An anti-aircraft shell has been fired and it has a kinetic energy\[x\]. It explodes in the air. Then the sum of kinetic energies of all the particles is
  A)
   \[x\] done clear
  B)
   more than \[x\]   done clear
  C)
   less than \[x\] done clear
  D)
   zero done clear
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• question_answer67)
  The kinetic energy acquired by a mass m after travelling a fixed distance from rest under the action of constant force is
  A)
   directly proportional to\[\sqrt{m}\] done clear
  B)
   directly proportional to m done clear
  C)
   independent of m   done clear
  D)
   directly proportional to \[\frac{1}{\sqrt{m}}\] done clear
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• question_answer68)
  A body of mass M collides against a wall with a velocity V and rebounds with the same speed. Its change of momentum is
  A)
   zero                      done clear
  B)
          \[MV\] done clear
  C)
   \[-2MV\]                              done clear
  D)
   \[-MV\] done clear
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• question_answer69)
  The power of a pump motor is 2 kilowatt. The water raised by the pump per minute to a height of 10 m is nearly
  A)
   500kg                   done clear
  B)
          7000kg done clear
  C)
   1200kg                   done clear
  D)
          zero done clear
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• question_answer70)
  A chain is held on a frictionless table with one third of its length hanging over the edge. The total length of the chain is 1 and its mass is m. The work required to pull the hanging part back to the table is
  A)
   \[2mgl\]              done clear
  B)
          \[\frac{mgl}{5}\] done clear
  C)
   \[\frac{mgl}{9}\]             done clear
  D)
          \[\frac{mgl}{18}\]   done clear
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• question_answer71)
  The bob of a simple pendulum (mass m and length1) dropped from a horizontal position strikes a block of the same mass elastically placed on a horizontally frictionless table. The K.E. of the block will be
  A)
   \[2mgl\]              done clear
  B)
          \[mgl/2\] done clear
  C)
   \[mgl\]                  done clear
  D)
          0 done clear
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• question_answer72)
  A mass M is attached to a massless spring of spring constant K. The mass is moved through a distance \[X\] and released. The maximum velocity of the mass is
  A)
   \[\frac{2\pi M}{K}\]       done clear
  B)
          \[\frac{K}{Mx}\,\frac{\sqrt{K}}{M}\]   done clear
  C)
   \[\frac{\sqrt{K}}{M}\]   done clear
  D)
          \[\frac{\sqrt{K}}{Mx}\] done clear
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• question_answer73)
  The kinetic energy of a body is numerically equal to thrice the momentum of the body. The velocity of the body is
  A)
   2 units            done clear
  B)
          3 units   done clear
  C)
   6 units            done clear
  D)
          9 units done clear
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• question_answer74)
  Which of the following is not a perfectly in elastic collision?
  A)
   Capture of an electron by proton done clear
  B)
   Man jumping on to a moving cart done clear
  C)
   Collision between glass balls   done clear
  D)
   A bullet fired into a block of wood such that it is embedded in the wood done clear
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• question_answer75)
  A body of mass m moving with velocity v suffers head on elastic collision with another body of mass 2 m at rest. The ratio of the kinetic energy off colliding body before and after collision is
  A)
   9:1                           done clear
  B)
          12:1            done clear
  C)
   16 : 1                     done clear
  D)
          18 : 1          done clear
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• question_answer76)
  A body of mass 2 kg is sliding with a constant velocity of 4 m/sec on a frictionless horizontal table. The force required to keep the body movie with the same velocity is
  A)
   \[8N\]                   done clear
  B)
          \[0\,N\]   done clear
  C)
   \[2\times {{4}^{2}}N\]                  done clear
  D)
   \[\frac{1}{2}N\] done clear
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• question_answer77)
  An open knife edge of mass M is dropped from a height h on a wooden floor. If the blade penetrates S into the wood, the average resistance offered by the wood to the blade is
  A)
   \[Mg\]                 done clear
  B)
          \[Mg\left( 1+\frac{h}{S} \right)\] done clear
  C)
   \[Mg(1+hS)\]    done clear
  D)
          \[mg{{\left( 1+\frac{h}{S} \right)}^{2}}\] done clear
  E)
         None of these done clear
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• question_answer78)
  Consider and elevator moving downwards with an acceleration a. The force exerted by a passenger of mass m on the floor of the elevator
  A)
   \[ma\]                 done clear
  B)
          \[ma-mg\] done clear
  C)
   \[mg-ma\]           done clear
  D)
          \[mg+ma\] done clear
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• question_answer79)
  A 60 kg man stands on a spring scale in a list At some instant he finds that the scale reading has changed from 60 kg to 50 kg for a while and then comes back to the original mark , What should he conclude?
  A)
   The lift was in constant motion upwards done clear
  B)
  The lift was in constant motion downwards done clear
  C)
   The lift while in motion upwards, suddenly stopped   done clear
  D)
   The lift while in motion downwards, suddenly stopped done clear
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• question_answer80)
  A lift is moving downwards with an acceleration equal to the acceleration due to gravity. A body of mass M kept on the floor of the lift is pulled horizontally. If the coefficient of friction is \[\mu \], then the friction resistance offered by the body is
  A)
   \[Mg\]                 done clear
  B)
          \[\mu Mg\] done clear
  C)
   \[2\mu Mg\]             done clear
  D)
          zero   done clear
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• question_answer81)
  In question No. 80, if the lift is moving upwards with a uniform velocity then the frictional resistance offered by the body is
  A)
   \[Mg\]                 done clear
  B)
          \[\mu Mg\]   done clear
  C)
   \[2\mu Mg\]             done clear
  D)
          zero done clear
  View Solution play_arrow

• question_answer82)
  Three particles A, B and C of equal mass, move with equal speed v along the medians of an equilateral triangle as shown in the figure. They collide at centroid G of the triangle. After collision, A comes to rest and B retracts its path with speed v. What is the speed of C after collision?
  A)
   Zero                      done clear
  B)
          \[\frac{\upsilon }{2}\] done clear
  C)
   \[v\]                       done clear
  D)
          \[2v\] done clear
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• question_answer83)
  A body of mass 1 kg rests on a smooth surface. Another body B of mass \[0.2\] kg is placed over A as shown. The coefficient of static between A and B is \[0.15\]. B will begin to slide on A if A is pulled with a force greater than   
  A)
   \[1.764N\]            done clear
  B)
          \[0.1764N\] done clear
  C)
   \[0.3N\]              done clear
  D)
          it will not slide for any F done clear
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• question_answer84)
  A person standing on the floor of an elevator drops a coin. The coin reaches the floor of the elevator in a time \[{{t}_{1}}\] if the elevator is stationary and in tune \[{{t}_{2}}\] if it is moving uniformly, then
  A)
   \[{{t}_{1}}={{t}_{2}}\]   done clear
  B)
   \[{{t}_{1}}>{{t}_{2}}\] done clear
  C)
   \[{{t}_{1}}<{{t}_{2}}\] done clear
  D)
   \[{{t}_{1}}<{{t}_{2}}\] or \[{{t}_{1}}>{{t}_{2}}\] depending on whether the left is going up or down. done clear
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• question_answer85)
  In a rocket, fuel burns at the rate of\[1\,Kg\,{{s}^{-1}}\]. This fuel is ejected from the rocket with a velocity of\[60\,Km{{s}^{-1}}\]. This exerts a force, in newton, on the rocket of
  A)
   \[60\,N\]              done clear
  B)
          \[600\,N\] done clear
  C)
   \[6,000\,N\]      done clear
  D)
          \[60,000\,N\]   done clear
  View Solution play_arrow

• question_answer86)
  A man has fallen into a ditch of width d and two of his friends are slowly pulling him out using a light rope and two fixed pulleys as shown in the figure. What is the force (assumed equal for both the friends) exerted by each friends on the slope?
  A)
   \[\frac{mg}{4h}\sqrt{{{d}^{2}}+4{{h}^{2}}}\]   done clear
  B)
          \[\frac{mg}{4h}\times d\] done clear
  C)
   \[\frac{mg}{4h}\times \sqrt{{{d}^{2}}+4{{h}^{2}}}\] done clear
  D)
          \[\frac{mgh}{d}\] done clear
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• question_answer87)
  The monkey B shown in figure, is holding on to the tail of the monkey A which is climbing up a rope. The masses of the monkeys A and B are 5 kg and 2 kg respectively. If A can tolerate a tension of 30 N in its tail, what force should it apply on the rope in order to carry the monkey B with it? Take \[\text{g }=\text{ 1}0\text{ m}/{{\text{s}}^{\text{2}}}\]
  A)
   between 50 N and \[80N\] done clear
  B)
   between 30 N and \[80N\] done clear
  C)
   between 70 N and \[150N\]   done clear
  D)
   between 60 N and \[90N\] done clear
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• question_answer88)
  A ball comes back after an elastic collision with a wall. If initial momentum of the ball is P, the impulse on the wall after the collision is
  A)
   \[P\]                     done clear
  B)
          \[2P\]   done clear
  C)
   zero                      done clear
  D)
          \[-2P\] done clear
  View Solution play_arrow

• question_answer89)
  A bullet of mass 10 gm moving with velocity of 100 m/sec hits a wooden log and penetrates it upto thickness of 5 cm. The resistance force of the log is
  A)
   \[200N\] done clear
  B)
   \[500N\] done clear
  C)
   \[1000N\]   done clear
  D)
   \[600N\] done clear
  View Solution play_arrow