May, 2022Flame Institute - Part 35

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Which one of the following is not a condensation polymer

a. Nylon 66 b. Nylon 6 c. Dacron d. Buna – S Ans. d (17)

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Perlon is

a. Rubber b. Nylon – 6 c. Terylene d. Orlon Ans. b (12)

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80. The earth E moves in an elliptical orbit with the sun S at one of the foci as shown in the figure. Its speed of motion will be maximum at the point

(a) C (b) A (c) B (d) D Ans. b (8)

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At what depth below the surface of the earth, acceleration due to gravity g will be half its value 1600 km above the surface of the earth

(a) 4.2 ×106 m (b) 3.19 × 106 m (c) 1.59 ×106m …

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Which of the following is not an example of addition polymer

a. Terylene b. Polypropylene c. Polyethylene d. Polystyrene Ans. a (9)

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Two planets of radii in the ratio 2 : 3 are made from the material of density in the ratio 3 : 2. Then the ratio of acceleration due to gravity g1/g2 at the surface of the two planets will be

(a) 1 (b) 2.25 (c) 4/9 (d) 0.12 Answer: a (6)

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Which polymers occur naturally

a. Starch and Nylon b. Starch and Cellulose c. Proteins and Nylon d. Proteins and PVC Ans. b (9)

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Which one is classified as a condensation polymer

a. Dacron b. Neoprene c. Teflon d. Acrylonitrile Ans. a (7)

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Which of the following is not correct regarding terylene

a. Step-growth polymer b. Synthetic fibre c. Condensation polymer d. It is also called decron e. Thermosetting plastic Ans. e (6)

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⌈NH (CH 2 ) NHCO (CH 2 ) 4 CO ⌉ n is a

⌈NH (CH 2 ) NHCO (CH 2 ) 4 CO ⌉ n is a a. Thermosetting polymer b. Homopolymer c. Copolyer d. Addition polymer Ans. c (11)

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The condensation polymer among the following is

a. Protein b. PVC c. Polythene d. Rubber Ans. a (11)

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Which of the following is not a synthetic polymer

a. Polyethylene b. PVC c. Nylon d. Cellophane Ans. d (7)

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If the density of a small planet is the same as that of earth, while the radius of the planet is 0.2 times that of the earth, the gravitational acceleration on the surface of that planet is

(a) 0.2 g (b) 0.4 g (c) 2 g (d) 4 g Answer: a (7)

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A body weight 500 N on the surface of the earth. How much would it weigh half way below the surface of the earth

(a) 125 N (b) 250 N (c) 500 N (d) 1000 N Answer: b (5)

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What should be the angular speed of earth, so that body lying on equator may appear weightlessness ( g = 10 m/s2, R=6400 km )

(a) 1/800 rad/s (b) 1/400 rad/s (c) 1/600 rad/s …

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A person will get more quantity of matter in kg –wt. at

(a) Poles (b) At latitude of 60o (c) Equator (d) Satellite Answer: d (12)

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89. A ball rolls without slipping. The radius of gyration of the ball about an axis passing through its centre of mass K. If radius of the ball be R, then the fraction of total energy associated with its rotational energy will be

(a) K2/R2 (b) K2/K2+R2 (c) R2/K2+R2 (d) K2+R2/R2 Ans. b (5)

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87. A stick of length l and mass M lies on a frictionless horizontal surface on which it is free to move in any way. A ball of mass m moving with speed v collides elastically with the stick as shown in the figure. If after the collision ball comes to rest, then what should be the mass of the ball

(a) m=2M (b) m=M (c) m=M/2 (d) m=m/4 Ans. d (10)

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A cubical block of side α is moving with velocity v on a horizontal smooth plane as shown. It hits a ridge at point O. The angular speed of the block after it hits O is

(a) 3v/4a (b) 3v/2a (c) √3v/√2a (d) Zero Ans. a (4)

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84. A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with an angular velocity ω . Another disc of same dimension but of mass M/4 is placed gently on the first disc coaxially. The angular velocity of the system now is

(a) 2ω/5 (b) 2ω/√5 (c) 4ω/5 (d) 4ω/√5 Ans. c (14)

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82. A uniform disc of mass M and radius R is rotating about a horizontal axis passing through its centre with angular velocity ω. A piece of mass m breaks from the disc and flies off vertically upwards. The angular speed of the disc will be

(a) (M-2m)ω/(M-m) (b) (M+2m)ω/(M+m) (c) (M-2m)ω/(M+m) (d) (M+2m)ω/(M-m) Ans. a (148)

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91. The total kinetic energy of a body of mass 10 kg and radius 0.5 m moving with a velocity of 2 m/s without slipping is 32.8 joule. The radius of gyration of the body is

(a) 0.25 m (b) 0.2 m (c) 0.5 m (d) 0.4 m Ans. d (37)

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88. In a playground there is a merry-go-round of mass 120 kg and radius 4 m. The radius of gyration is 3m. A child of mass 30 kg runs at a speed of 5 m/sec tangent to the rim of the merry-go-round when it is at rest and then jumps on it. Neglect friction and find the angular velocity of the merry-go-round and child

(a) 0.2 rad/sec (b) 0.1 rad/sec (c) 0.4 rad/sec (d) 0.8 rad/sec Ans. c (74)

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83. A particle undergoes uniform circular motion. About which point on the plane of the circle, will the angular momentum of the particle remain conserved

(a) Centre of the circle (b) On the circumference of the circle (c) Inside the circle (d) Outside the circle Ans. a (5)

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81. A rigid spherical body is spinning around an axis without any external torque. Due to change in temperature, the volume increases by 1%. Its angular speed

(a) Will increase approximately by 1% (b) Will decrease approximately by 1% (c) Will decrease approximately by 0.67% (d) Will decrease approximately by 0.33% Ans. c (7)

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A thin circular ring of mass M and radius r is rotating about its axis with a constant angular velocity ω. Two objects each of mass m are attached gently to the opposite ends of a diameter of the ring. The ring will now rotate with an angular velocity

(a) ω(M-2m) /(M+2m) (b) ωM/M+2m) (c) ωM/M+m (d) ω(M+2m)/M Ans. b (39)

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78. An equilateral triangle ABC formed from a uniform wire has two small identical beads initially located at A. The triangle is set rotating about the vertical axis AO. Then the beads are released from rest simultaneously and allowed to slide down, one along AB and the other along AC as shown. Neglecting frictional effects, the quantities that are conserved as the beads slide down, are

(a) Angular velocity and total energy (kinetic and potential) (b) Total angular momentum and total energy (c) Angular velocity and moment of inertia about the axis of rotation (d) Total angular momentum and moment of inertia about …

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77. A uniform heavy disc is rotating at constant angular velocity ω about a vertical axis through its centre and perpendicular to the plane of the disc. Let L be its angular momentum. A lump of plasticine is dropped vertically on the disc and sticks to it. Which will be constant

(a) w (b) w and L both (c) L only (d) Neither w nor L Ans. c (45)

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76.

Two rigid bodies A and B rotate with rotational kinetic energies EA and EB respectively. The moments of inertia of A and B about the axis of rotation are IA and IB respectively. If IA = IB /4 and EA …

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75. A particle of mass m moves along line PC with velocity v as shown. What is the angular momentum of the particle about O

(a) mvL (b) mvl (c) mvr (d) Zero Ans. b (3)

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The density of a newly discovered planet is twice that of earth. The acceleration due to gravity at the surface of the planet is equal to that at the surface of the earth. If the radius of the earth is R, the radius of the planet would be

(a) 2R (b) 4R (c) 1/4 R …

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74. A disc is rotating with an angular speed of ω. If a child sits on it, which of the following is conserved

(a) Kinetic energy (b) Potential energy (c) Linear momentum (d) Angular momentum Ans. d (11)

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73. The motion of planets in the solar system is an example of the conservation of

(a) Mass (b) Linear momentum (c) Angular momentum (d) Energy Ans. c (7)

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If both the mass and the radius of the earth decrease by 1%, the value of the acceleration due to gravity will

(a) Decrease by 1% (b) Increase by 1% (c) Increase by 2% (d) Remain unchanged Answer: b (8)

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73. Weight of a body of mass m decreases by 1% when it is raised to height h above the earth’s surface. If the body is taken to a depth h in a mine, change in its weight is

(a) 2% decrease (b) 0.5% decrease (c) 1% increase (d) 0.5% increase Answer: b (6)

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The depth at which the effective value of acceleration due to gravity is g/4 is

(a) R (b) 3R/4 (c) R/2 (d) R/4 Answer: b (4)

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72. A thin rod of length L and mass M is bent at the middle point O at an angle of 60 degree as shown in figure. The moment of inertia of the rod about an axis passing through O and perpendicular to the plane of the rod will be

(a) ML2/6 (b) ML2/12 (c) ML2/24 (d) ML2/3 Ans. b (23)

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71. The acceleration of a body due to the attraction of the earth (radius R) at a distance 2 R from the surface of the earth is (g = acceleration due to gravity at the surface of the earth)

(a) g/9 (b) g/3 (c) g/4 …

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Acceleration due to gravity on moon is 1/6 of the acceleration due to gravity on earth. If the ratio of densities of earth ( pe ) and moon ( pm ) is ( pe/pm ) = 5/3 then radius of moon Rm in terms of Re will be

(a) 5/18 Re (b) 1/6 Re (c) 3/18 Re (d) 1/2√3 Re Answer: …

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71. The moment of inertia I of a solid sphere having fixed volume depends upon its volume V as

(a) I ∝ V (b) I ∝ V2/3 (c) I ∝ V5/3 (d) I ∝ V3/2 Ans. c (10)

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