# work energy and power class 11 numericals with solutions

*Dear students in this page contains **work energy and power class 11 numericals with solutions pdf. It also contains pdf for neet questions of chapter 6 **work energy and power** 11 jee questions, aiims important questions at one place to get you all prepared for your neet, aiims ,jee main, advance exams as well as cbse board exams and other board exams. Visit my nawendu classes youtube channel for more help.*

1. If momentum is increased by 20% then kinetic energy increased by

**AFMC 1997**

Answer- 44%

2. If the momentum of a body is increased by 50% , then the percentage increase in its kinetic energy is

**CBSE AIPMT 1995**

Answer- 125%

3. If the kinetic energy of a body is increased by 300% , then the percentage change in its momentum will be

**CBSE AIPMT 2002**

Answer- 100%

4. The mass of two substances are 25g and 81g respectively. If their kinetic energies are same then the ratio of their momentum is

**AFMC 2000**

Answer- 5:9

5. Two bodies of masses ‘m’ and ‘4m’ are moving with equal kinetic energy. Then the ratio of their linear momentum will be

**AIIMS 1999**

Answer- 1:2

6.Two bodies with kinetic energies in the ratio 4:1 are moving with equal linear momentum. The ratio of their masses is

**CBSE AIPMT 1999**

Answer- 1:4

7. A stationary particle explodes into two particles of masses \[{{m}_{1}}\]and ${{m}_{2}}$,which move in opposite directions with velocities ${{v}_{1}}$and ${{v}_{2}}$.The ratio of their kinetic energies$\frac{{{E}_{1}}}{{{E}_{2}}}$ IS

**CBSE AIPMT 2003**

Answer- $\frac{{{m}_{2}}}{{{m}_{1}}}$

8.If a man increases his speed by 2m/s, his Kinetic energy is doubled. The original speed of the man is

Answer- $\left( 2+2\sqrt{2} \right)m/s$

9.A body is displaced from $x={{x}_{1}}$ to $x={{x}_{2}}$ by a force 2x. The work done is

**CPMT 1993**

Answer- $x_{2}^{2}-x_{1}^{2}$

10.A particle moves from a point (-2i+5j) to (4j+3k) when a force of (4i+3j) N is applied. How much work has been done by the force ?

Answer- 5J

11.A position dependent force, \[~F=\text{ }\left(
7-2x+3{{x}^{2}} \right)\]N acts on a small body of mass 2 kg and displaces it from x =0 to x=5 m. Work done in joule is

**CBSE AIPMT 1992**

Answer- 135

12. A uniform force of $\left( 3\hat{i}+\hat{j} \right)N$ acts on a particle of mass 2 kg. Hence, the particle is displaced from position $\left( 2\hat{i}+\hat{k} \right)m$ to position $\left( 4\hat{i}+3\hat{j}-\hat{k} \right)m$. The work done by the force on the particle is

**NEET 2013**

Answer- 9J

13.A body of mass 5kg has momentum of 10kg m/s. When a force of 0.2N is applied on it for 10s, the change in its kinetic energy is

**AIIMS 2000**

Answer- 4.4J

14. If a body of mass 3kg is dropped from the top of a tower of height 25m. Then its kinetic energy after 3 sec is

**AFMC 1998**

Answer- 735J

15. The particle of 50 kg is at rest. The work done to accelerate it by 20m/s in 10 s is

**AIIMS 2012**

Answer- ${{10}^{4}}$J

16.A block of mass 10kg is moving in x-direction with a constant speed of 10 m/s. It is subjected to a retarding force F=-0.1 x joule/meter during its travel from x=20 meter to x=30 meter. Its final kinetic energy will be

**AIIMS 2005**

Answer- 475J

17.A particle of mass 10g is thrown vertically upwards with a speed of 5 m/s. The work done by the force of gravity during the time the particle goes up is

**AIEEE 2006**

Answer- 0.125J

18. A ball is released from the top of a tower ,the ratio of work done by force of gravity in first ,second and third second of the motion of the ball is

**AIIMS 2005**

Answer- 1:3:5

19. A spherical ball of mass 20kg is stationary at the top of a hill of height 100m. It rolls down a smooth surface to the ground ,then climbs up another hill of height 30m and finally rolls down to a horizontal base at a height of 20m above the ground. The velocity attained by the ball is

**AIIMS 2006**

Answer- 40m/s

20. A bullet of mass m moving with velocity v strikes a suspended wooden lock of mass M. If the block rises to a height h ,the initial velocity of the block will be

**AIIMS 2013**

Answer- \[\sqrt{2gh}\]

21. A body of mass 5 kg is raised vertically to a height of 10 m by a force of 170 N .The velocity of the body at this height will be

**AIIMS 1998**

Answer- 22m/s

22. A body of mass 3kg is under a constant force, which causes a displacement s in metre in it,given by the relation s=$\frac{1}{3}{{t}^{2}}$ , where t is in second ,work done by the force in 2s is

**CBSE AIPMT 2006**

Answer- 8/3 joule

23. A body of mass 2kg is projected vertically upwards with speed of 3m/s. The maximum gravitational potential energy of the body is

Answer- 9J

24. If a water falls from a dam into a turbine wheel 19.6 below, then the velocity of water at the turbines is (take g=9.8m/s2 )

**AIIMS 2007**

Answer- 19.6m/s

25.A body of mass 1 kg is thrown upwards with a velocity 20 m/s. It momentarily comes to rest after attending a height of 18m. How much energy is loss due to air friction (g=10m/s2)

**CBSE AIPMT 2009**

Answer- 20J

26. 300J of work is done in sliding a 2kg block up an inclined plane of height 10m.Taking g=10 $m/{{s}^{2}}$,work done against friction is

**CBSE AIPMT 2006**

Answer- 100 joule

27. Two springs of spring constant 1500 N/m and 3000 N/m respectively are stretched with the same force. They will have the potential energies in the ratio of

**AFMC 2000**

Answer- 2:1

28. A spring of force constant 10 N per meter has an initial has an initial stretch 0.20 m. In changing the stretch to 0.25m, the increase in potential energy is about

Answer- 0.1

29. A spring of spring constant 5 x 103 N/m is stretched initially by 5cm from the unscratched position. Then the work required to stretch it further by another 5 cm is

**AIEEE 2003**

Answer- 18..75Nm

30. A spring 40mm long is stretched by applying a force . If10 N force is required to stretched the spring through 1mm,then work done in stretching the spring through 40mm is

**AIIMS 2001**

Answer- 8J

31. A car is moving with constant speed of 20 m/s against a resistance of 100N. The power exerted by the car is

Answer- 2KW

32. An electric motor creates a tension of 4500N in a hoisting cable and reels it at the rate of 2 m/s. What is the power of the electric motor

Answer- 9KW

33. How much water, a pump of 2kw can rise in one minute to height of 10m, taking g=10 m/s2

**CBSE AIPMT 1990**

Answer- 1200 liters

34. Water falls from a height of 60m at the rate of 15kg/s to operate a turbine. The losses due to frictional force are 10% of energy. How much power is generated by the turbine? (g=10 m/s2 )

Answer- 8.1KW

35. A particle of mass m is driven by a machine that delivers a constant power k watts. If the particle starts from rest ,the force on the particle at time t is

**CBSE AIPMT 2015**

Answer- $\sqrt{\frac{mk}{2}}{{t}^{\frac{-1}{2}}}$

36.A stone is tied to a string of length l and is whirled in a vertical circle with the other end of the string as the center .At a certain instant of time ,the stone is at its lowest position and has a speed u. The magnitude of the change in velocity as it reaches a position where the string is horizontal (g being acceleration due to gravity ) is

**CBSE AIPMT 2004**

Answer- $\sqrt{2\left( {{u}^{2}}-gl \right)}$

37.A uniform chain of length 2m is kept on a table such that a length of 60cm hangs freely from the edge of the table. The total mass of the chain is 4 kg. What is the work done in pulling the entire chain on the table ?

**AIEEE 2004**

Answer- 3.6J

38.A block of mass m moving with speed v collides with another block of mass 2m at rest. The lighter block comes to rest after collision. What is the value of coefficient of restitution

Answer- 1/2

39. A body of mass 10kg and velocity 10m/s collides with a stationary body of mass 5kg. After collision both bodies stick to each other, velocity of the bodies after collision will be.

**AFMC 1997**

Answer- \[\frac{20}{3}m{{s}^{-1}}\]

40. Two identical balls A and B having velocities of 0.5m/s and -0.3m/s respectively collide elastically in one dimension. The velocities of B and A after the collision respectively will be

**NEET 2016**

Answer- -0.3m/s and 0.5m/s

41. A object of mass 40kg having velocity 4 m/s collides with another object m=60 kg having velocity 2 m/s. The collision is perfectly inelastic. The loss in energy is

**AFMC 2001**

Answer- 48J

42.A ball moving with velocity 2m/s collides head on with another stationary ball of double the mass. If coefficient of restitution is 0.5, then their velocities after collision will be

**CBSE AIPMT 2010**

Answer- 0,1

43.A block of mass 0.5 kg is moving with a speed of 2.0m/s on smooth surface. It strikes another mass of 1.0kg and then they move together as a single body. The energy loss during collision is

**AIEEE 2008**

Answer- 0.67J

44.A ball falls under gravity from height 10 m with an initial velocity u. It hits the ground, loss 50% of the energy in collision and it rises to the same height. What is the value of u

Answer- 14m/s

45. A ball is thrown vertically downwards from a height of 20m with an initial velocity \[{{v}_{0}}\] .It collides with the ground, loses 50% of its energy in collision and rebounds to the same height. The initial velocity \[{{v}_{0}}\] is (take g= 10 $m{{s}^{-2}}$)

**CBSE AIPMT 2015**

Answer- 20m/s

46. A force F acting on an object varies with distance x as shown here. The force is in newton and x is in metre. The work done by the force in moving the object from x=0 to x=6m is

**CBSE AIPMT 2005**

Answer- 13.5J

47. A body of mass 1 kg is thrown upwards with a velocity 20m/s. It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction

**CBSE AIPMT 2009**

Answer- 20 joule

48. Consider a drop of rain water having mass 1g falling from a height of 1km. It hits the ground with a speed of 50m/s. Take g constant with a value of 10 $m/{{s}^{2}}$. The work done by (i) gravitational force and the (ii) resistive force of air is

**NEET 2017**

Answer- (i) 10 J (ii) -8.75 J

49. A block of mass M is attached to the lower end of a vertical spring .The spring is hung from a ceiling and has force constant value k. The mass is released from rest with the spring initially unstretched . The maximum extension produced in the length of the spring will be

**CBSE AIPMT 2009**

Answer- $\frac{2Mg}{k}$

50. The potential energy of a particle in a force field is $U=\frac{A}{{{r}^{2}}}-\frac{B}{r}$ ,where A and B are positive constants and r is the distance of particle from the center of the field. For stable equilibrium ,the distance of the particle is

**CBSE AIPMT 2012**

Answer- $\frac{2A}{B}$

51. On a frictionless surface, a block of mass M moving at speed v collides elastically with another block of same mass M which is initially at rest. After collision the first block moves at an angle $\theta $ to its initial direction and has a speed v/3.The second block’s after the collision is

**CBSE AIPMT 2015**

Answer- $\frac{2\sqrt{2}}{3}v$

52. A particle of mass 10g moves along a circle of radius 6.4 cm with a constant tangential acceleration. What is the magnitude of this acceleration , if the kinetic energy of the particle becomes equal to $8\times {{10}^{-4}}$ J by the end of the second revolution after the beginning of the motion ?

**NEET 2016**

Answer- $0.m/{{s}^{2}}$

53. What is the minimum velocity with which a body of mass m must enter a vertical loop of radius R so that it can complete the loop ?

**NEET 2016**

Answer- $\sqrt{5gR}$

54. A body of mass 1kg begins to move under the action of a time dependent force \[\vec{F}=\left( 2t\hat{i}+3{{t}^{2}}\hat{j} \right)N\],where $\hat{i}$and$\hat{j}$ are unit vectors along X and Y axes . What power will be developed by the force at the time t ?

**NEET 2016**

Answer- $\left( 2{{t}^{3}}+3{{t}^{5}} \right)W$

55. A person of mass 70 kg wants to loss 7 kg by moving up and down on the stairs of 12m height . Assume he burns twice as much fat while going up than going down. If 1 kg of fat is burnt on expending 9000kcal. How many times must he go up and down to reduce his 7kg weight ?

**AIIMS 2016**

Answer- $21\times {{10}^{3}}$ times

56. The particle of mass m is moving in a circular path of constant radius r such that its centripetal acceleration ${{a}_{c}}$ is varying with time t as ${{a}_{c}}={{k}^{2}}r{{t}^{2}}$,where k is a constant. The power delivered to particle by the force acting on it is

**AIIMS 2017**

Answer- $m{{k}^{2}}{{r}^{2}}t$

57. A time dependant force F=6t acts on a particle of mass 1 kg. If the particle starts fro rest ,the work done by the force during the first 1 s will be

**IIT 2017 Main**

Answer- 4.5 J

58. A block of mass 2kg is free to move along the x axis. It is at rest and from t=0 onwards it is subjected to a time dependent force $F\left( t \right)$ in the x direction .The force $F\left( t \right)$ varies with t as shown in the figure. The kinetic energy of the block after 4.5 s is

**IIT 2010**

Answer- 5.06 J

59. A uniform cable of mass M and length L is placed on a horizontal surface such that its (\[\frac{1}{n}\])th part is hanging below the edge of the surface. To lift the hanging part of the cable upto the surface, the work done should be

**IIT 2019 Main 9 April I**

Answer- $\frac{MgL}{2{{n}^{2}}}$

60. A block of mass m is kept on a platform which starts from rest with constant acceleration g/2 upwards as shown in figure. Work done by normal reaction on block in time t is

**IIT 2019 Main 10 Jan I**

Answer- $\frac{3m{{g}^{2}}{{t}^{2}}}{8}$

61. A force acts on 2kg object , so that its position is given as a function of time as x = 3t2+ 5. What is the work done by this force in first 5 seconds?

**IIT 2019 Main 9 Jan II**

Answer- 900 J

62. A particle is moving in a circular path of radius a under the action of an attractive potential energy $U=-\frac{k}{{{r}^{2}}}$ . Its total energy is

IIT 2018 Main

Answer- Zero

63. When a rubber band is stretched by a distance x, it exerts a restoring force magnitude $F=ax+b{{x}^{2}}$ , where a and b are constants. The work done in stretching the upstretched rubber band by L is

**IIT 2014 Main**

Answer- $\frac{a{{L}^{2}}}{2}+\frac{b{{L}^{3}}}{3}$

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