Tiêu đề NT 15 PAPER.pdf ✅

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10. An elevator weighing 3000 kg is pulled upwards by a cable with an acceleration of 5 ms–2 . Taking g to be 10 ms–2 . Then the tension in the cable is- (A) 6000 N (B) 9000 N (C) 60000 N (D) 45000 N 11. The elevator shown in figure is descending, with an acceleration of 2 ms–2 . The mass of the block A is 0.5 kg. The force exerted by the block A on the block B is : A B –2 2ms (A) 2 N (B) 4 N (C) 6 N (D)8 N 12. In the figure shown, blocks A and B move with velocities v1 and v2 along horizontal direction. The ratio of 1 2 v v : A 1 B v 2 v 1  2  (A) 2 1 sin sin   (B) 1 2 sin sin   (C) 2 1 cos cos   (D) 1 2 cos cos   13. A block of mass m = 2 kg is resting on a rough inclined plane of inclination 300 as shown in figure. The coefficient of friction between the block and the plane is μ = 0.5. What minimum force F should be applied perpendicular to the plane on the block, so that block does not slip on the plane (g=10m/s2 ) A F 30o (A) zero (B) 6.24 N (C) 2.68 N (D) 4.34 N 14. A body A of mass M is kept on a rough horizontal surface (friction coefficient = μ). A person is trying to pull the body by applying a horizontal force but the body is not moving. The force by the surface on A is F where- (A) F = Mg (B) F = μMg (C) Mg  F  Mg 2 1+ (D) Mg  F  Mg 2 1–  15. A box 'A' is lying on the horizontal floor of the compartment of a train running along horizontal rails from left to right. At time 't', it decelerates. Then the reaction R by the floor on the box is given best by : (A) R A floor (B) R A floor (C) A floor R (D) A floor R 16. The earth (Me = 6 × 1024 kg) is revolving round the sun in an orbit of radius (1.5 × 108 ) km with angular velocity of (2 × 10–7 ) rad/s. The force (in newton) exerted on the earth by the sun will be :- (A) 36 × 1021 (B) 16 × 1024 (C) 25 × 1016 (D) Zero 17. A motor cycle driver doubles its velocity when he is taking a turn. The force exerted towards the centre will become :- (A) double (B) half (C) 4 times (D) 1 4 18. A block of mass m is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration a. The work done by tension on the block during t seconds is (u = 0) : (A) m 2 (g + a) at2 (B) m 2 (g – a)at2 (C) m 2 gat2 (D) 0