CBSE Class 11 Physics Newton laws of Motion Objective Questions

OBJECTIVES

1. A boy of mass 60 kg is holding a vertical rope. The rope can break when a mass of 75 kg is suspended from it. The maximum acceleration with which the boy can climb the rope without breaking it is
(a) 2.5 m/s² (b) 5.0 m/s² (c) 7.5 m/s² (d) 22.5 m/s²

2. A pendulum with a bob of 0.1 kg is suspended from the roof of a car which is moving with an acceleration of 5 m/s² relative to the ground towards right. An observer travelling in the car experiences a pseudo force acting on the bob equal to
(a) 1.0 Newton downwards (b) 1.0 Newton upwards (c) 0.5 Newton towards right (d) 0.5 Newton towards left

3. The mass of an elevator is 4000 kg. Starting from rest how much distance will it rise in 2 s, if the tension in the cable is 56 kN?
(a) 3 m (b) 4 m (c) 8 m (d) 16 m

4. The weights W and 2W are suspended from the ends of a light string passing over a smooth fixed pulley. If the pulley is pulled with an acceleration of 10 m/s², the tension in the string will be
(a) W/3  (b) 2W/3   (c) 4W/3  (d) 8W/3

5. A pendulum having from the ceiling of a railway carriage makes an angle of 30º with the vertical when it is accelerating. The acceleration of the carriage in m/s² is
(a) 10/√3 (b) 20/√3  (c) 5 √3 (d) 10 √3 

6. Two masses of 5 kg and 10 kg are suspended from a fixed support as shown in the figure. The system is pulled downwards with a force of 150 N applied to the lower mass. The string attached to the support breaks and the system accelerates downwards. If the downward force continues to act, the acceleration of the system is

(a) 5 m/s² (b) 10 m/s² (c) 20 m/s² (d) 30 m/s² 

7. Two masses m and 3m are connected as shown in the figure. The tension in the string is3mm30º

(a) 3mg/4  (b) 9mg/8  (c) mg (d) 2mg

8. A block of mass 1.0 kg rests on a wedge of angle θ. The acceleration which should be given to the wedge so that the block falls freely is

(a) 10 m/s² (b) 10 cos θ m/s² (c) 10 cot θ m/s² (d) 10 tan θ m/s²

9. Three equals weights A, B, C of mass 2 kg each are hanging on a string passing over a fixed frictionless pulley as shown in the figure. The tension in the string connecting weights B and C is
(a) 6.6 N (b) 13.3 N A B (c) 19.6 N (d) 26.6 N

10. Two masses of 10 kg and 20 kg are connected with an inextensible string passing over two smooth pulleys as shown in the figure. The acceleration of 20 kg mass will be

(a) 10/3 m/s² (b) 20/3 m/s²  (c) 40/9 m/s ² (d) 10 m/s²

11. The weights w₁ and w₂ are suspended from the ends of a light strig passing over a smooth fixed pulley. If the pulley is pulled up with an acceleration g, the tension in the string will be
(a)w₁w₂/w₁+w₂  (b)  2w₁w₂/w₁+w₂    (c) 4w₁w₂/w₁+w₂  (d)  w₁w₂/2(w₁+w₂₎
12. Two blocks each of mass m are connected over two light and frictionless pulleys by a light string as shown in figure. The tension in the string is

(a) 2 mg sin θ (b) 3/2 mg sin θ m θ m (c) 2mgsin θ/3  (d) mgsinθ/2

13. A pendulum is hanging from the ceiling of a railway carriage subtending an angle of 30º with the vertical direction. The acceleration of the carriage is
(a) g/√3 (b) 2g/√3  (c) g√3  (d) √3 g/2