Unique Practice Questions Physics Unit 1 Mechanics Corporate Office Aakash Tower 8 Pusa Road New Delhi 110005 Ph 011 47623456 Unique Practice Questions Answers 1 2 3 4 5 6 7 8 9 4 2 4 4 4 3 3 1 4 10 2 11 1 12 2 13 2 14 4 15 3 16 3 17 1 18 3 19 4 20 1 21 4 22 4 23 4 24 25 Aakash Educational Services Limited Corporate Office Aakash Tower 8 Pusa Road New Delhi 110005 8 Unique Practice Questions Physics Unit 1 Mechanics 1 Answer 4 4 Answer 4 Initial angular acceleration before it slips off Solution Angular speed acquire by the box in time From a rotating frame rod will appear in equilibrium Net torque about suspension point t 3g 2I 0 01 3 10 0 01 1 2 2 0 3 rad sec dx x sin x cos Mg sin 2 The angle by which it would rotate when hits cos mg I I 2 3g 2I 0 01 s the ground t Assuming w constant and t time of fall 2H g 1 sec radians 1 2 2 Answer 2 W man Mg eff l g eff g 1 2 0 W man Mgl 1 2 0 3 Answer 4 tA tB t vA a1 tB t a2tB v i S a t 1 B 2 t a t 2 2 B 1 2 1 2 t 1B t ii a 2 a 1 Solving i and ii v t a a 1 2 L 2 must be zero L 0 M L 3g 2 2l 5 Answer 4 I M 2 R 4 2 L 12 M R2L I M M 2 L 4 L 12 0 3 L 6 M 4 dI dL 3 L LR 2 L R 6 4 3 2 6 Answer 3 at a depth r a 1 a 2 R E r Gm 3 R E Gm r R E 2 r R E GM 2 R E 1 GM 2 2 E R 1 r R E Aakash Educational Services Limited Corporate Office Aakash Tower 8 Pusa Road New Delhi 110005 9 Unique Practice Questions Physics Unit 1 Mechanics VA I 2 Vd 4 I V V 2 d d I I 2 0 01 5 0 1 0 01 0 1 5 10 2 0 039 3 9 13 Answer 2 E 1 1 2 v 2 rel 1 m 2 2 2 v 2 mv 1 4 Velocity after collision v 2 E 2 1 2 2 2 m M v m M 2 2 E 1 E 2 5 1 6 2 2 mv 1 m 2 2 2 v 1 m 2 2 2 v M 2 m M 5 1 6 2 2 mv 1 M 2 m M 10 6 5 3 4 M m 14 Answer 4 1 a 1 a 2 1 2 r R E r R E 3 r 3 R E 2 1 r R E r 2 R E at a height r 7 Answer 3 9 K K 3 Y 9 3 Y Y K 8 Answer 1 2M V2 M m u m M 1 V 2 2 M M u 2 u 9 Answer 4 t 2 l v 2 t l v 1 v 2 t t t 1 2 t t 1 2 l l t 2 l t 1 Let l be the length of escalator v1 be the velocity of man w r t escalator v2 be the velocity of escalator l v t 1 1 10 Answer 2 Weight of the person becomes zero only once Hence option 2 is correct 11 Answer 1 Net force on M is towards A hence torque is zero about A cons tan t AL 12 Answer 2 V I A s1 s2 h 4 3h 4 Time of collision t 0 h 2gh h 2g Aakash Educational Services Limited Corporate Office Aakash Tower 8 Pusa Road New Delhi 110005 10 Unique Practice Questions Physics Unit 1 Mechanics s 1 1 2 gt 2 0 1 2 g h h 2g 4 I 2 a 4 A Ba 5 4 17 Answer 1 Speed of A just before collision v1 And speed of B just before collision v2 s 2 3h 4 gt 0 gh 2 2gh gh 2 After collision velocity of centres of mass m 2gh V cm gh 2 2m m gh 2 0 So from there time of fall t 3h 4 2 gt 1 2 t 3 h 2 g 15 Answer 3 2mvx mu mu cos 60 vx 3u 4 Horizontal range after collision 3u 4 2H g 2 3 3u 8g 16 Answer 3 I 2 dmr 2 2 rdr r I 2 A Br r dr 2 3 4 Aa 4 5 Ba 5 a 0 2 mu 1 2 GMm 1 2 R 2 mv GMm 2R 1 2 v 2 m v 2 u GMm 2R 2 GM u R i v 0 GM 2R v rad 10 v m v m 10 9m GM m 10 2R 10 v 2 v 81 GM 2R KE rocket 1 m 2 10 2 u GM R 100 81 GM 2R m 20 2 100 u GM 81 GM R 200 R 5m u 2 119 GM 200 R 18 Answer 3 h h0e2 81 100 2 e e 0 9 Stotal h0 2h1 2h2 2h3 h0 1 2 e2 e4 e6 h 1 2 e 0 2 1 1 e 2 h 0 2 2 1 e 1 e Ttotal 1 2 e 2e 2 1 2e 1 1 e 1 1 e 1 e 02h g 2 5 10 Aakash Educational Services Limited Corporate Office Aakash Tower 8 Pusa Road New Delhi 110005 11 Unique Practice Questions Physics Unit 1 Mechanics V av 2 5 1 0 9 2 1 0 9 1 0 9 1 0 9 2 50 m s bcos a a M m 19 Answer 4 T f mgsin60 0 p 1 bcos 3a i As 2 M m and for block mgsin macos mb b gsin 2 cos b 3 b 1 2 cos gsin 1 3 T 2R mgsin60 R T mg 3 4 from 1 and 2 2 mg 3 mg 3 mg 3 2 4 4 f f f max max f s mg mg 5 2 f mg 5 20 Answer 1 As xF 0 acom 0 M a m bcos a 0 b g 1 2 1 1 3 3 4 2 3 g 21 Answer 4 1 2 dr dt 2 3 t 2 mv m GM r 0 v 2GM r 2GM r R e h R e t 0 r dr 2GM dt R e 3 2 h R 3 2 e 2GM t 2R1 3 g e 1 h R e 3 2 1 22 Answer 4 Let N drop sec V 1 g 1 N H 0 1 2 g 1 N 2 At t 4 s 9 8 4 4 9 34 3 N 1 1 …