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NCERT Solutions › Physics › Chapter 6

Chapter 6: Work Energy & Power

NCERT Solutions for CBSE Class 10 Physics — 105 solved questions with detailed explanations.

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Solved Questions

Q1. A body of mass 2 kg is moving with velocity 10 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½ × 2 × 100 = 100 J.

Q2. An elastic collision is one in which:

Difficulty: Easy · Topic: Collisions

Solution

In an elastic collision, both linear momentum and kinetic energy are conserved.

Q3. A body of mass 2 kg moves with velocity 5 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×2×5² = 25 J.

Q4. A body of mass 3 kg moves with velocity 10 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×3×10² = 150 J.

Q5. A body of mass 4 kg moves with velocity 6 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×4×6² = 72 J.

Q6. A body of mass 5 kg moves with velocity 8 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×5×8² = 160 J.

Q7. A body of mass 1 kg moves with velocity 20 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×1×20² = 200 J.

Q8. A body of mass 10 kg moves with velocity 4 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×10×4² = 80 J.

Q9. A body of mass 6 kg moves with velocity 5 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×6×5² = 75 J.

Q10. A body of mass 8 kg moves with velocity 3 m/s. Its kinetic energy is:

Difficulty: Easy · Topic: Kinetic Energy

Solution

KE = ½mv² = ½×8×3² = 36 J.

Q11. KE of 1kg body at 1m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*1²=0.5 J.

Q12. KE of 1kg body at 2m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*2²=2.0 J.

Q13. KE of 1kg body at 3m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*3²=4.5 J.

Q14. KE of 1kg body at 4m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*4²=8.0 J.

Q15. KE of 1kg body at 5m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*5²=12.5 J.

Q16. KE of 1kg body at 6m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*6²=18.0 J.

Q17. KE of 1kg body at 7m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*7²=24.5 J.

Q18. KE of 1kg body at 8m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*8²=32.0 J.

Q19. KE of 1kg body at 9m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*9²=40.5 J.

Q20. KE of 1kg body at 10m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*10²=50.0 J.

Q21. KE of 1kg body at 11m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*11²=60.5 J.

Q22. KE of 1kg body at 12m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*12²=72.0 J.

Q23. KE of 1kg body at 13m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*13²=84.5 J.

Q24. KE of 1kg body at 14m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*14²=98.0 J.

Q25. KE of 1kg body at 15m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*15²=112.5 J.

Q26. KE of 1kg body at 16m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*16²=128.0 J.

Q27. KE of 1kg body at 17m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*17²=144.5 J.

Q28. KE of 1kg body at 18m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*18²=162.0 J.

Q29. KE of 1kg body at 19m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*19²=180.5 J.

Q30. KE of 1kg body at 20m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*20²=200.0 J.

Q31. KE of 1kg body at 21m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*21²=220.5 J.

Q32. KE of 1kg body at 22m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*22²=242.0 J.

Q33. KE of 1kg body at 23m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*23²=264.5 J.

Q34. KE of 1kg body at 24m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*1*24²=288.0 J.

Q35. KE of 2kg body at 1m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*1²=1.0 J.

Q36. KE of 2kg body at 2m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*2²=4.0 J.

Q37. KE of 2kg body at 3m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*3²=9.0 J.

Q38. KE of 2kg body at 4m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*4²=16.0 J.

Q39. KE of 2kg body at 5m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*5²=25.0 J.

Q40. KE of 2kg body at 6m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*6²=36.0 J.

Q41. KE of 2kg body at 7m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*7²=49.0 J.

Q42. KE of 2kg body at 8m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*8²=64.0 J.

Q43. KE of 2kg body at 9m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*9²=81.0 J.

Q44. KE of 2kg body at 10m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*10²=100.0 J.

Q45. KE of 2kg body at 11m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*11²=121.0 J.

Q46. KE of 2kg body at 12m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*12²=144.0 J.

Q47. KE of 2kg body at 13m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*13²=169.0 J.

Q48. KE of 2kg body at 14m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*14²=196.0 J.

Q49. KE of 2kg body at 15m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*15²=225.0 J.

Q50. KE of 2kg body at 16m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*16²=256.0 J.

Q51. KE of 2kg body at 17m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*17²=289.0 J.

Q52. KE of 2kg body at 18m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*18²=324.0 J.

Q53. KE of 2kg body at 19m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*19²=361.0 J.

Q54. KE of 2kg body at 20m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*20²=400.0 J.

Q55. KE of 2kg body at 21m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*21²=441.0 J.

Q56. KE of 2kg body at 22m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*22²=484.0 J.

Q57. KE of 2kg body at 23m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*23²=529.0 J.

Q58. KE of 2kg body at 24m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*2*24²=576.0 J.

Q59. KE of 3kg body at 1m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*1²=1.5 J.

Q60. KE of 3kg body at 2m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*2²=6.0 J.

Q61. KE of 3kg body at 3m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*3²=13.5 J.

Q62. KE of 3kg body at 4m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*4²=24.0 J.

Q63. KE of 3kg body at 5m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*5²=37.5 J.

Q64. KE of 3kg body at 6m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*6²=54.0 J.

Q65. KE of 3kg body at 7m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*7²=73.5 J.

Q66. KE of 3kg body at 8m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*8²=96.0 J.

Q67. KE of 3kg body at 9m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*9²=121.5 J.

Q68. KE of 3kg body at 10m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*10²=150.0 J.

Q69. KE of 3kg body at 11m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*11²=181.5 J.

Q70. KE of 3kg body at 12m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*12²=216.0 J.

Q71. KE of 3kg body at 13m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*13²=253.5 J.

Q72. KE of 3kg body at 14m/s:

Difficulty: Easy · Topic: KE

Solution

KE=½mv²=0.5*3*14²=294.0 J.

Q73. A spring of spring constant 200 N/m is compressed by 0.1 m. The potential energy stored is:

Difficulty: Easy-Medium · Topic: Elastic PE

Solution

PE = ½kx² = ½ × 200 × 0.01 = 1 J.

Q74. A force F = 5i + 3j N acts on a body which displaces it by d = 2i + 4j m. The work done is:

Difficulty: Easy-Medium · Topic: Work Done

Solution

W = F·d = 5(2) + 3(4) = 10 + 12 = 22 J.

Q75. A pump lifts 200 kg of water to a height of 10 m in 20 s (g = 10 m/s²). The power of the pump is:

Difficulty: Easy-Medium · Topic: Power

Solution

P = mgh/t = 200 × 10 × 10/20 = 1000 W.

Q76. A spring (k=100 N/m) compressed by 10 cm stores PE of:

Difficulty: Easy-Medium · Topic: Spring PE

Solution

PE = ½kx² = ½×100×0.1² = 0.5 J.

Q77. A spring (k=200 N/m) compressed by 5 cm stores PE of:

Difficulty: Easy-Medium · Topic: Spring PE

Solution

PE = ½kx² = ½×200×0.05² = 0.25 J.

Q78. A spring (k=400 N/m) compressed by 2 cm stores PE of:

Difficulty: Easy-Medium · Topic: Spring PE

Solution

PE = ½kx² = ½×400×0.02² = 0.08 J.

Q79. A spring (k=50 N/m) compressed by 20 cm stores PE of:

Difficulty: Easy-Medium · Topic: Spring PE

Solution

PE = ½kx² = ½×50×0.2² = 1.0 J.

Q80. A spring (k=500 N/m) compressed by 4 cm stores PE of:

Difficulty: Easy-Medium · Topic: Spring PE

Solution

PE = ½kx² = ½×500×0.04² = 0.4 J.

Q81. A pump lifts 100 kg of water to height 20 m in 10 s. Power is (g=10 m/s²):

Difficulty: Easy-Medium · Topic: Power

Solution

P = mgh/t = 100×10×20/10 = 2000 W.

Q82. A pump lifts 200 kg of water to height 10 m in 20 s. Power is (g=10 m/s²):

Difficulty: Easy-Medium · Topic: Power

Solution

P = mgh/t = 200×10×10/20 = 1000 W.

Q83. A pump lifts 50 kg of water to height 40 m in 25 s. Power is (g=10 m/s²):

Difficulty: Easy-Medium · Topic: Power

Solution

P = mgh/t = 50×10×40/25 = 800 W.

Q84. A pump lifts 500 kg of water to height 5 m in 10 s. Power is (g=10 m/s²):

Difficulty: Easy-Medium · Topic: Power

Solution

P = mgh/t = 500×10×5/10 = 2500 W.

Q85. A pump lifts 150 kg of water to height 20 m in 15 s. Power is (g=10 m/s²):

Difficulty: Easy-Medium · Topic: Power

Solution

P = mgh/t = 150×10×20/15 = 2000 W.

Q86. A body of mass 1 kg falls from height 10 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×10) = 14.14 m/s.

Q87. A body of mass 2 kg falls from height 15 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×15) = 17.32 m/s.

Q88. A body of mass 3 kg falls from height 20 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×20) = 20.0 m/s.

Q89. A body of mass 4 kg falls from height 25 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×25) = 22.36 m/s.

Q90. A body of mass 5 kg falls from height 30 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×30) = 24.49 m/s.

Q91. A body of mass 6 kg falls from height 35 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×35) = 26.46 m/s.

Q92. A body of mass 7 kg falls from height 40 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×40) = 28.28 m/s.

Q93. A body of mass 8 kg falls from height 45 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×45) = 30.0 m/s.

Q94. A body of mass 9 kg falls from height 50 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×50) = 31.62 m/s.

Q95. A body of mass 10 kg falls from height 55 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×55) = 33.17 m/s.

Q96. A body of mass 11 kg falls from height 60 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×60) = 34.64 m/s.

Q97. A body of mass 12 kg falls from height 65 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×65) = 36.06 m/s.

Q98. A body of mass 13 kg falls from height 70 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×70) = 37.42 m/s.

Q99. A body of mass 14 kg falls from height 75 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×75) = 38.73 m/s.

Q100. A body of mass 15 kg falls from height 80 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×80) = 40.0 m/s.

Q101. A body of mass 16 kg falls from height 85 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×85) = 41.23 m/s.

Q102. A body of mass 17 kg falls from height 90 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×90) = 42.43 m/s.

Q103. A body of mass 18 kg falls from height 95 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×95) = 43.59 m/s.

Q104. A body of mass 19 kg falls from height 100 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×100) = 44.72 m/s.

Q105. A body of mass 20 kg falls from height 105 m. Its velocity just before hitting ground is (g=10):

Difficulty: Easy-Medium · Topic: Energy Conservation

Solution

v = √(2gh) = √(2×10×105) = 45.83 m/s.

Other Chapters in Physics

Ch 1: Physical WorldCh 2: Units & MeasurementsCh 3: Motion in a Straight LineCh 4: Motion in a PlaneCh 5: Laws of MotionCh 7: System of ParticlesCh 8: GravitationCh 9: Mechanical Properties of SolidsCh 10: Mechanical Properties of FluidsCh 11: Thermal Properties of MatterCh 12: ThermodynamicsCh 13: Kinetic TheoryCh 14: OscillationsCh 15: Waves

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