Chapter 5: Laws of Motion
NCERT Solutions for CBSE Class 10 Physics — 105 solved questions with detailed explanations.
Solved Questions
Q1. According to Newton's third law, action and reaction forces:
- Act on the same body
- Act on different bodies
- Need not be equal
- Act along different lines
Difficulty: Easy · Topic: Newton's Third Law
Solution
Action and reaction forces always act on two different bodies. They are equal in magnitude and opposite in direction.
Q2. A net force of 10 N acts on a body of mass 2 kg. The acceleration is:
- 4 m/s²
- 5 m/s²
- 7 m/s²
- 10 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 10/2 = 5 m/s².
Q3. A net force of 20 N acts on a body of mass 5 kg. The acceleration is:
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 20/5 = 4 m/s².
Q4. A net force of 50 N acts on a body of mass 10 kg. The acceleration is:
- 5 m/s²
- 4 m/s²
- 7 m/s²
- 10 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 50/10 = 5 m/s².
Q5. A net force of 15 N acts on a body of mass 3 kg. The acceleration is:
- 4 m/s²
- 5 m/s²
- 7 m/s²
- 10 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 15/3 = 5 m/s².
Q6. A net force of 24 N acts on a body of mass 4 kg. The acceleration is:
- 8 m/s²
- 5 m/s²
- 6 m/s²
- 12 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 24/4 = 6 m/s².
Q7. A net force of 40 N acts on a body of mass 8 kg. The acceleration is:
- 7 m/s²
- 5 m/s²
- 10 m/s²
- 4 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 40/8 = 5 m/s².
Q8. A net force of 30 N acts on a body of mass 6 kg. The acceleration is:
- 4 m/s²
- 10 m/s²
- 7 m/s²
- 5 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 30/6 = 5 m/s².
Q9. A net force of 5 N acts on a body of mass 1 kg. The acceleration is:
- 5 m/s²
- 4 m/s²
- 10 m/s²
- 7 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 5/1 = 5 m/s².
Q10. A net force of 35 N acts on a body of mass 7 kg. The acceleration is:
- 4 m/s²
- 5 m/s²
- 7 m/s²
- 10 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 35/7 = 5 m/s².
Q11. A net force of 60 N acts on a body of mass 12 kg. The acceleration is:
- 7 m/s²
- 4 m/s²
- 10 m/s²
- 5 m/s²
Difficulty: Easy · Topic: Newton's Second Law
Solution
a = F/m = 60/12 = 5 m/s².
Q12. Force 5 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=5/1=5.0 m/s².
Q13. Force 10 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=10/1=10.0 m/s².
Q14. Force 15 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=15/1=15.0 m/s².
Q15. Force 20 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=20/1=20.0 m/s².
Q16. Force 25 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=25/1=25.0 m/s².
Q17. Force 30 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=30/1=30.0 m/s².
Q18. Force 35 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=35/1=35.0 m/s².
Q19. Force 40 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=40/1=40.0 m/s².
Q20. Force 45 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=45/1=45.0 m/s².
Q21. Force 50 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=50/1=50.0 m/s².
Q22. Force 55 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=55/1=55.0 m/s².
Q23. Force 60 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=60/1=60.0 m/s².
Q24. Force 65 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=65/1=65.0 m/s².
Q25. Force 70 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=70/1=70.0 m/s².
Q26. Force 75 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=75/1=75.0 m/s².
Q27. Force 80 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=80/1=80.0 m/s².
Q28. Force 85 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=85/1=85.0 m/s².
Q29. Force 90 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=90/1=90.0 m/s².
Q30. Force 95 N on mass 1 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=95/1=95.0 m/s².
Q31. Force 5 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=5/2=2.5 m/s².
Q32. Force 10 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=10/2=5.0 m/s².
Q33. Force 15 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=15/2=7.5 m/s².
Q34. Force 20 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=20/2=10.0 m/s².
Q35. Force 25 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=25/2=12.5 m/s².
Q36. Force 30 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=30/2=15.0 m/s².
Q37. Force 35 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=35/2=17.5 m/s².
Q38. Force 40 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=40/2=20.0 m/s².
Q39. Force 45 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=45/2=22.5 m/s².
Q40. Force 50 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=50/2=25.0 m/s².
Q41. Force 55 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=55/2=27.5 m/s².
Q42. Force 60 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=60/2=30.0 m/s².
Q43. Force 65 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=65/2=32.5 m/s².
Q44. Force 70 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=70/2=35.0 m/s².
Q45. Force 75 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=75/2=37.5 m/s².
Q46. Force 80 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=80/2=40.0 m/s².
Q47. Force 85 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=85/2=42.5 m/s².
Q48. Force 90 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=90/2=45.0 m/s².
Q49. Force 95 N on mass 2 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=95/2=47.5 m/s².
Q50. Force 5 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=5/3=1.67 m/s².
Q51. Force 10 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=10/3=3.33 m/s².
Q52. Force 15 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=15/3=5.0 m/s².
Q53. Force 20 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=20/3=6.67 m/s².
Q54. Force 25 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=25/3=8.33 m/s².
Q55. Force 30 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=30/3=10.0 m/s².
Q56. Force 35 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=35/3=11.67 m/s².
Q57. Force 40 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=40/3=13.33 m/s².
Q58. Force 45 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=45/3=15.0 m/s².
Q59. Force 50 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=50/3=16.67 m/s².
Q60. Force 55 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=55/3=18.33 m/s².
Q61. Force 60 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=60/3=20.0 m/s².
Q62. Force 65 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=65/3=21.67 m/s².
Q63. Force 70 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=70/3=23.33 m/s².
Q64. Force 75 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=75/3=25.0 m/s².
Q65. Force 80 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=80/3=26.67 m/s².
Q66. Force 85 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=85/3=28.33 m/s².
Q67. Force 90 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=90/3=30.0 m/s².
Q68. Force 95 N on mass 3 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=95/3=31.67 m/s².
Q69. Force 5 N on mass 4 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=5/4=1.25 m/s².
Q70. Force 10 N on mass 4 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=10/4=2.5 m/s².
Q71. Force 15 N on mass 4 kg. Acceleration:
Difficulty: Easy · Topic: Newton II
Solution
a=F/m=15/4=3.75 m/s².
Q72. A body of mass 5 kg is acted upon by two perpendicular forces of 12 N and 5 N. The acceleration of the body is:
- 2.6 m/s²
- 3.4 m/s²
- 1.0 m/s²
- 0.4 m/s²
Difficulty: Easy-Medium · Topic: Newton's Second Law
Solution
F_net = √(12²+5²) = √(144+25) = 13 N. a = F/m = 13/5 = 2.6 m/s².
Q73. A monkey of mass 40 kg climbs a rope with an acceleration of 2 m/s². The tension in the rope is (g = 10 m/s²):
Difficulty: Easy-Medium · Topic: Apparent Weight
Solution
T - mg = ma. T = m(g+a) = 40(10+2) = 480 N.
Q74. A block of mass 10 kg is placed on a rough horizontal surface (μ = 0.3). The force required to just move the block is (g = 10 m/s²):
Difficulty: Easy-Medium · Topic: Friction
Solution
F = μmg = 0.3 × 10 × 10 = 30 N.
Q75. A lift is moving downward with acceleration g. The apparent weight of a person inside the lift is:
Difficulty: Easy-Medium · Topic: Lift Problems
Solution
Apparent weight = m(g-a). When a = g, apparent weight = m(g-g) = 0 (weightlessness).
Q76. A person of mass 50 kg is in a lift accelerating upward at 2 m/s². The apparent weight is (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Lift Problems
Solution
Apparent weight = m(g+a) = 50(10+2) = 600 N.
Q77. A person of mass 60 kg is in a lift accelerating upward at 3 m/s². The apparent weight is (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Lift Problems
Solution
Apparent weight = m(g+a) = 60(10+3) = 780 N.
Q78. A person of mass 40 kg is in a lift accelerating downward at 2 m/s². The apparent weight is (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Lift Problems
Solution
Apparent weight = m(g-a) = 40(10-2) = 320 N.
Q79. A person of mass 70 kg is in a lift accelerating upward at 1 m/s². The apparent weight is (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Lift Problems
Solution
Apparent weight = m(g+a) = 70(10+1) = 770 N.
Q80. A person of mass 80 kg is in a lift accelerating downward at 2 m/s². The apparent weight is (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Lift Problems
Solution
Apparent weight = m(g-a) = 80(10-2) = 640 N.
Q81. A block of mass 5 kg on a horizontal surface (μ=0.2) requires what force to just start moving? (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Friction
Solution
F = μmg = 0.2×5×10 = 10.0 N.
Q82. A block of mass 10 kg on a horizontal surface (μ=0.3) requires what force to just start moving? (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Friction
Solution
F = μmg = 0.3×10×10 = 30.0 N.
Q83. A block of mass 20 kg on a horizontal surface (μ=0.4) requires what force to just start moving? (g=10 m/s²):
- 160.0 N
- 40.0 N
- 85.0 N
- 80.0 N
Difficulty: Easy-Medium · Topic: Friction
Solution
F = μmg = 0.4×20×10 = 80.0 N.
Q84. A block of mass 8 kg on a horizontal surface (μ=0.25) requires what force to just start moving? (g=10 m/s²):
Difficulty: Easy-Medium · Topic: Friction
Solution
F = μmg = 0.25×8×10 = 20.0 N.
Q85. A block of mass 15 kg on a horizontal surface (μ=0.5) requires what force to just start moving? (g=10 m/s²):
- 75.0 N
- 80.0 N
- 150.0 N
- 37.5 N
Difficulty: Easy-Medium · Topic: Friction
Solution
F = μmg = 0.5×15×10 = 75.0 N.
Q86. Two blocks of masses 2 kg and 4 kg are connected by a string on a frictionless surface. A force of 18 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q87. Two blocks of masses 3 kg and 5 kg are connected by a string on a frictionless surface. A force of 24 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q88. Two blocks of masses 4 kg and 6 kg are connected by a string on a frictionless surface. A force of 30 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q89. Two blocks of masses 5 kg and 7 kg are connected by a string on a frictionless surface. A force of 36 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q90. Two blocks of masses 6 kg and 8 kg are connected by a string on a frictionless surface. A force of 42 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q91. Two blocks of masses 7 kg and 9 kg are connected by a string on a frictionless surface. A force of 48 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q92. Two blocks of masses 8 kg and 10 kg are connected by a string on a frictionless surface. A force of 54 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q93. Two blocks of masses 9 kg and 11 kg are connected by a string on a frictionless surface. A force of 60 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q94. Two blocks of masses 10 kg and 12 kg are connected by a string on a frictionless surface. A force of 66 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q95. Two blocks of masses 11 kg and 13 kg are connected by a string on a frictionless surface. A force of 72 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q96. Two blocks of masses 12 kg and 14 kg are connected by a string on a frictionless surface. A force of 78 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q97. Two blocks of masses 13 kg and 15 kg are connected by a string on a frictionless surface. A force of 84 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q98. Two blocks of masses 14 kg and 16 kg are connected by a string on a frictionless surface. A force of 90 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q99. Two blocks of masses 15 kg and 17 kg are connected by a string on a frictionless surface. A force of 96 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q100. Two blocks of masses 16 kg and 18 kg are connected by a string on a frictionless surface. A force of 102 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q101. Two blocks of masses 17 kg and 19 kg are connected by a string on a frictionless surface. A force of 108 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q102. Two blocks of masses 18 kg and 20 kg are connected by a string on a frictionless surface. A force of 114 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q103. Two blocks of masses 19 kg and 21 kg are connected by a string on a frictionless surface. A force of 120 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q104. Two blocks of masses 20 kg and 22 kg are connected by a string on a frictionless surface. A force of 126 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
Q105. Two blocks of masses 21 kg and 23 kg are connected by a string on a frictionless surface. A force of 132 N is applied. The tension in the string is:
Difficulty: Medium · Topic: Connected Bodies
Solution
a = F/(m1+m2). T = m2×a.
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