Newton's Laws of Motion PYQs Set 3 (PDF)

Set 3 of 7 · Questions 61-90 of 197

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Mere Teacher · Previous Year Questions JEE Main Physics · Newton's Laws of Motion · Set 3 (Q61-90)
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61. $One end of string of length l is connected to a particle of mass m and the other end is connected to a small peg on a smooth horizontal table. If the particle moves in circle with speed v, the net force on the particle (directed towards centre) will be (T represents the tension in the string)$ (1) $T + \frac{m ν ^{2}}{l}$ (2) $T - \frac{m ν ^{2}}{l}$ (3) $zero$ (4) $T$ 62. $A stone of mass 0.05 kg is thrown vertically upwards. What is the direction and magnitude of net force on the stone during its upward motion?$ (1) $0.49 N vertically downwards.$ (2) $9.8 N vertically downwards.$ (3) $0.49 N vertically upwards.$ (4) $0.98 N vertically downwards.$ 63. $Force is the mutual interaction between the bodies is according to$ (1) $Newton's first law of motion$ (2) $Newton's second law of motion.$ (3) $Newton's third law of motion$ (4) $Newton's law of gravitation$ 64. $The mass of a lift is 2000 kg . When the tension in the supporting cable is 28000 N, then its acceleration is$ (1) $4 m s^{- 2} upwards$ (2) $4 m s^{- 2} downwards$ (3) $14 m s^{- 2} upwards$ (4) $30 m s^{- 2} downwards$ 65. $The force required to stop a body of mass 10 kg moving along a straight line path with a velocity of 10 ms^{- 1} in a time of 10 s is$ (1) $10 N$ (2) $1000 N$ (3) $100 N$ (4) $1 N$ 66. $A force of 6Nacts on a body at rest and of mass 1 kg. During this time, the body attains a velocity of 30 m/s. The time for which the force acts on the body is$ (1) $7 seconds$ (2) $5 seconds$ (3) $10 seconds$ (4) $8 seconds$ 67. $A truck of mass 2000 kg is moving along a circular path having radius of curvature 10 m . if the banking angle is 39^{\circ}, then the maximum permissible speed of the truck is (Acceleration due to gravity = 10 ms^{- 2}, take tan 39^{\circ} = 0.81)$ (1) $14 ms^{- 1}$ (2) $5 ms^{- 1}$ (3) $18 ms^{- 1}$ (4) $9 ms^{- 1}$ 68. $A person of mass 60 kg is inside a lift of mass 940 kg and presses the button on control panel. The lift starts moving upwards with an acceleration 1.0 m/ s^{2} . If g = 10 m s^{- 2}, the tension in the supporting cable is:$ (1) $8600 N$ (2) $9680 N$ (3) $11000 N$ (4) $1200 N$ 69. $The magnitude of the external force acting on moving bodies can be known directly by$ (1) $Law of conservation of angular momentum$ (2) $Newton's first law of motion.$ (3) $Newton's second law of motion.$ (4) $Law of conversation of energy.$ 70. $A person of 60 kg mass is in a lift which is coming down such that the man exerts a force of 150 N on the floor of the lift. Then the acceleration of the lift is (g = 10 ms^{- 2})$ (1) $7.5 ms^{- 2}$ (2) $40.0 ms^{- 2}$ (3) $22.5 ms^{- 2}$ (4) $15.0 ms^{- 2}$ 71. $A light string passing over a smooth light pulley connects two blocks of masses m_{1} and m_{2} (where m_{2} > m_{1}). If the acceleration of the system is \frac{g}{2}, then the ratio of the masses \frac{m _{1}}{m _{2}} is:$ (1) $\frac{1 + 5}{5 - 1}$ (2) $\frac{3 + 1}{2 - 1}$ (3) $\frac{2 - 1}{2 + 1}$ (4) $\frac{1 + 5}{2 - 1}$ 72. $When a bullet is fired from a rifle its momentum becomes 20 kg ms^{- 1} . If the velocity of the bullet is 1000 ms^{- 1}, then what is its mass?$ (1) $30 g$ (2) $5 kg$ (3) $20 g$ (4) $500 g$ 73. $A 4 kg mass moves under the influence of a force F = (4 t^{3} i - 3 t j) N where t is the time in second. If mass starts from origin at t = 0, the velocity and position after t = 2 s will be:$ (1) $v = 4 i - \frac{3}{2} j, r = \frac{6}{5} i - j$ (2) $v = 3 i + \frac{3}{2} j, r = \frac{6}{5} i + j$ (3) $v = 4 i - \frac{3}{2} j, r = \frac{8}{5} i - j$ (4) $v = 4 i + \frac{5}{2} j, r = \frac{8}{5} i + 2 j$ 74. $A particle moves in a circle with speed v varying with time as v (t) = 2 t . The total acceleration of the particles after it completes 2 rounds of cycle is$ (1) $16 π$ (2) $2 1 + 64 π^{2}$ (3) $2 1 + 49 π$ (4) $14 π$ 75. $A man weighing 60 kg is in a lift moving down with an acceleration of 1.8 m s^{- 2} . The force exerted by the floor on him is$ (1) $588 N$ (2) $480 N$ (3) $zero$ (4) $696 N$ 76. $A body falls on a surface of coeflicient of restitution 0.6 from a height of 1 m . Then the body rebounds to a height of$ (1) $1 m$ (2) $0.36 m$ (3) $0.4 m$ (4) $0.6 m$ 77. $A car is moving in a circular horizontal track of radius 10 m with a constant speed of 10 m s^{- 1} . A bob is suspended from the roof of the car by a light wire of length 1.0 m . The angle made by the wire with the vertical is (in radian)$ (1) $0$ (2) $\frac{π}{6}$ (3) $\frac{π}{3}$ (4) $\frac{π}{4}$ 78. $A cricketer catches a ball of mass 150 gm in 0.1 sec moving with speed 20 m / s, then he experiences force of$ (1) $300 N$ (2) $30 N$ (3) $3 N$ (4) $0.3 N.$ 79. $Which one of the following statements is incorrect? [NEET 2018]$ (1) $Frictional force opposes the relative motion$ (2) $Limiting value of static friction is directly proportional to normal reaction$ (3) $Rolling friction is smaller than sliding friction$ (4) $Coefficient of sliding friction has dimensions of length$ 80. $Two forces whose magnitudes are in the ratio 5:3 are acting at a point at an angle 60^{\circ} simultaneously. If the resultant of the two forces is 35 N, then the magnitudes of two forces respectively are$ (1) $3 N, 5 N$ (2) $25 N, 9 N$ (3) $25 N, 15 N$ (4) $12 N, 20 N$ 81. $A coin placed on a rotating table just slips when it is placed at a distance of 1 cm from the centre. If the angular velocity of the table is halved, it will just slip when placed at a distance of_____from the centre:$ (1) $8 cm$ (2) $4 cm$ (3) $1 cm$ (4) $2 cm$ 82. $A wire of length L is hanging from a fixed support. The length changes to L_{1} and L_{2} when masses 1kg and 2 kg are suspended respectively from its free end. Then the value of L is equal to:$ (1) $L_{1} L_{2}$ (2) $\frac{L _{1} + L _{2}}{2}$ (3) $2 L_{1} - L_{2}$ (4) $3 L_{1} - 2 L_{2}$ 83. $In the arrangement shown in figure a_{1}, a_{2}, a_{3} and a_{4} are the accelerations of masses m_{1}, m_{2}, m_{3} and m_{4} respectively. Which of the following relation is true for this arrangement?$ (1) $4 a_{1} + 2 a_{2} + a_{3} + a_{4} =0$ (2) $a_{1} + 4 a_{2} + 3 a_{3} + a_{4} =0$ (3) $a_{1}_{+} 4 a_{2}_{+} 3 a_{3}_{+} 2 a_{4} =0$ (4) $2 a_{1}_{+} 2 a_{2} + 3 a_{3} + a_{4} =0$ 84. $A rigid ball of mass m strikes a rigid wall at 60^{\circ} and gets reflected without loss of speed as shown in the figure. The value of impulse imparted by the wall on the ball will be [NEET 2016]$ (1) $mv$ (2) $2 mv$ (3) $mv /2$ (4) $mv /3$ 85. $A book is lying on a table. What is the angle between the normal reaction acting on the book on the table and the weight of the book?$ (1) $0^{\circ}$ (2) $45^{\circ}$ (3) $90^{\circ}$ (4) $180^{\circ}$ 86. $A stone of mass 900 g is tied to a string and moved in a vertical circle of radius 1 m making 10 rpm . The tension in the string, when the stone is at the lowest point is (if π^{2} = 9.8 and g = 9.8 m / s^{2})$ (1) $97 N$ (2) $9.8 N$ (3) $8.82 N$ (4) $17.8 N$ 87. $A heavy iron bar, of weight W is having its one end on the ground and the other on the shoulder of a person. The bar makes an angle θ with the horizontal. The weight experienced by the person is:$ (1) $Wsin θ$ (2) $W$ (3) $\frac{W}{2}$ (4) $Wcos θ$ 88. $The resultant of two forces acting an angle of 120^{\circ} is 10 kg wt and is perpendicular to one of the forces. That force is$ (1) $103 kgwt$ (2) $203 kgwt$ (3) $10 kgwt$ (4) $\frac{10}{3} kgwt$ 89. $A 1 kg stationary bomb is exploded in three parts having mass 1: 1: 3 respectively Parts having same mass move in perpendicular direction with velocity 30 m / s, then the velocity of bigger part will be$ (1) $102 m / s$ (2) $\frac{10}{2} m / s$ (3) $152 m / s$ (4) $\frac{15}{2} m / s$ 90. $The sum of two forces P \to and Q \to is R \to such that \| R \to \| = \| P \to \| The angle θ (in degrees) that the resultant of 2 P \to and Q \to will make with Q \to is$