Title 2. Low of motion (M.C.Q. ) E.pdf ✅

wedge and ground. Friction is absent everywhere. Select the correct alternative(s) - m M  (A) N2 < (M + m) g (B) N1 = m (g cos  – | a | 1  sin ) (C) N1 sin  = M | a | 1  (D) m  2 a = – M  1 a Sol. [A, B, C] Q. 16 A particle of mass 70 g moving at 50 cm/s, is acted upon by a variable force opposite to direction of its motion. Force F is shown as a function of time 't' – (in Newton) 10 4×10–3 8×10 t (in sec) –3 10–2 F (A) It speed will 50 cm/sec after the force stop acting (B) Its direction of motion will reverse (C) It average acceleration will be 1 m/s2 , during the interval force acts (D) Its average acc. will be 10m/s2 , during the interval in which force act Sol.[A,B] Change in momentum = – (area under curve ) Q. 17 It block of mass 1 kg moves under influence of external force on a rough horizontal surface. At some instant, it has a speed of 1 m/s due east and acceleration is 1m/s2 due north. The friction force acting on it is 'F' – (A) F acts due west (B) F acts due south (C) F acts in south-west direction (D) The magnitude of F cannot be found from the given data Sol.[A,D] friction force opposes relative slipping Q. 18 Two blocks A and B of equal mass m are connected through a massless string and arranged as shown in figure. Friction is absent everywhere. When the system is released from rest – 30o A Fixed B (A) tension in string is 2 mg (B) tension in string is 4 mg (C) acceleration of A is 2 g (D) acceleration of A is 4 3 g Sol.[B,D] a = (m m) (m m/ 2)g   = g 4 3  T = mg – 4 3mg = 4 mg (Block B) Q. 19 A block of mass 1 kg is at rest relative to a smooth wedge moving leftwards with constant acceleration a = 5 m/s2 . Let N be the normal reaction between the block and the wedge. Then – (g = 10 m/s2 )  a 1 kg (A) N = 5 5 N (B) N = 15 N (C) tan  = 2 1 (D) tan = 2 Sol.[A,C] N = mg cos + ma sin a = g tan tan = 1⁄2 Q.20 A block of mass 1 kg moves under the influence of external forces on a rough horizontal surface. At some instant, it has a speed of 1 m/s due east and an acceleration of 1 m/s2 due north. The force of friction acting on it is F - (A) F acts due west (B) F acts due south (C) F acts in the south-west direction (D) The magnitude of F cannot be found from the given data Sol. [A,D] oppose the relative velocity Q.21 A block of mass m is placed on a rough horizontal surface. The coefficient of friction between them is . An external horizontal force is applied to the block and its magnitude is