Practice Questions

Q16.A rocket with a lift-off mass 3.5 × 104 kg is blasted upwards with an initial acceleration of 10 m/s2 . Then the initial thrust of the blast is (1) 3.5 × 105 N (2) 7.0 × 105 N (3) 14.0 × 105 N (4) 1.75 × 105 N

Q17.Consider the following two statements: (A) Linear momentum of a system of particles is zero (B) Kinetic energy of a system of particles is zero Then (1) A does not imply B and B does not imply A (2) A implies B but B does not imply A (3) A does not imply B but B implies A (4) A implies B and B implies A

Q18.A spring of spring constant 5 × 103 N/m is stretched initially by 5 cm from the unstretched position. Then the work required to stretch it further by another 5 cm is (1) 12.50 N −m (2) 18.75 N −m (3) 25.00 N −m (4) 6.25 N −m

Q19.A body is moved along a straight line by a machine delivering a constant power. The distance moved by the body in time ' t ' is proportional to (1) t3/4 (2) t3/2 (3) t1/4 (4) t1/2

Q20.A circular disc X of radius R is made from an iron plate of thickness t, and another disc Y of radius 4R is made from an iron plate of thickness t . Then the relation between the moment of inertia IX and IY is 4 (1) IY = 32Ix (2) IY = 16Ix (3) IY = IX (4) IY = 64IX

Q21.A particle performing uniform circular motion has angular frequency is doubled \& its kinetic energy halved, then the new angular momentum is (1) L (2) 2 L 4 (3) 4 L (4) L2

Q22.Let →F be the force acting on a particle having position vector →r and →T be the torque of this force about the origin. Then → → → → → → (1)→r⋅ T = 0 and F. T ≠0 (2)→r⋅ T ≠0 and F ⋅ T = 0 → → → → → → (3)→r⋅ T ≠0 and F ⋅ T ≠0 (4)→r⋅ T = 0 and F ⋅ T = 0

Q23.The time period of a satellite of earth is 5 hours. If the separation between the earth and the satellite is increased to 4 times the previous value, the new time period will become JEE Main 2003 JEE Main Previous Year Paper (1) 10 hours (2) 80 hours (3) 40 hours (4) 20 hours

Q24.Two spherical bodies of mass M and 5M& radii R&2R respectively are released in free space with initial separation between their centres equal to 12R. If they attract each other due to gravitational force only, then the distance covered by the smaller body just before collision is (1) 2.5R (2) 4.5R (3) 7.5R (4) 1.5R

Q25.The escape velocity for a body projected vertically upwards from the surface of earth is 11 km/s. If the body is projected at an angle of 45∘ with the vertical, the escape velocity will be (1) 11√2 km/s (2) 22 km/s (3) 11 km/s (4) 11 km/s √2

Q26.A wire suspended vertically from one of its ends is stretched by attaching a weight of 200 N to the lower end. The weight stretches the wire by 1 mm. Then the elastic energy stored in the wire is (1) 0.2 J (2) 10 J (3) 20 J (4) 0.1 J

Q27.The earth radiates in the infra-red region of the spectrum. The spectrum is correctly given by (1) Rayleigh Jeans law (2) Planck's law of radiation (3) Stefan's law of radiation (4) Wien's law

Q28.According to Newton's law of cooling, the rate of cooling of a body is proportional to (Δθ)n , where Δθ is the difference of the temperature of the body and the surroundings, and n is equal to (1) two (2) three (3) four (4) one Q29."Heat cannot by itself flow from a body at lower temperature to a body at higher temperature" is a statement or consequence of (1) second law of thermodynamics (2) conservation of momentum (3) conservation of momentum (4) first law of thermodynamics

Q30.Which of the following parameters does not characterize the thermodynamic state of matter? (1) temperature (2) Pressure (3) Work (4) Volume

Q31.A Carnot engine takes 3 × 106cal. of heat from a reservoir at 627∘C, and gives it to a sink at 27∘C. The work done by the engine is (1) 4.2 × 106 J (2) 8.4 × 106 J (3) 16.8 × 106 J (4) Zero

Q32.During an adiabatic process, the pressure of a gas is found to be proportional to the cube of its absolute temperature. The ratio Cp/Cv for the gas is JEE Main 2003 JEE Main Previous Year Paper (1) 4 (2) 2 3 (3) 5 (4) 3 3 2

Q33.In the nuclear fusion reaction 21H + 31H →42He + n given that the repulsive potential energy between the two nuclei is ∼7.7 × 10−14 J, the temperature at which the gases must be heated to initiate the reaction is nearly [Boltzmann's Constant k = 1.38 × 10−23 J/K ] (1) 107 K (2) 105 K (3) 103 K (4) 109 K

Q34.A mass M is suspended from a spring of negligible mass. The spring is pulled a little and then released so that the mass executes SHM of time period T. If the mass is increased by m, the time period becomes 53T . Then the ratio of Mm is (1) 53 (2) 259 (3) 16 (4) 5 9 3

Q35.Two particles A and B of equal masses are suspended from two massless springs of spring constant k1 and k2 , respectively. If the maximum velocities, during oscillation, are equal, the ratio of amplitude of A and B is (1) (2) k2 k1 √k1k2 k2 (3) √k2k1 (4) k1

Q36.The displacement of a particle varies according to the relation x = 4(cos πt + sin πt). The amplitude of the particle is (1) −4 (2) 4 (3) 4√2 (4) 8

Q37.A body executes simple harmonic motion. The potential energy (P.E), the kinetic energy (K.E) and total energy (T.E) are measured as a function of displacement x. Which of the following statements is true? (1) K.E. is maximum when x = 0 (2) T.E is zero when x = 0 (3) K.E is maximum when x is maximum (4) P.E. is maximum when x = 0

Q38.The displacement y of a wave travelling in the x-direction is given by y = 10−4 sin (600t −2x + π3 ) metres where x is expressed in metres and t in seconds. The speed of the wave-motion, in ms−1 , is (1) 300 (2) 600 (3) 1200 (4) 200

Q39.A tuning fork of known frequency 256 Hz makes 5 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was (1) 256 + 2 Hz (2) 256 −2 Hz (3) 256 −5 Hz (4) 256 + 5 Hz

Q40.If the electric flux entering and leaving an enclosed surface respectively is ϕ1 and ϕ2 , the electric charge inside the surface will be JEE Main 2003 JEE Main Previous Year Paper (1) (ϕ2 −ϕ1)ε0 (2) (ϕ1 + ϕ2)/ε0 (3) (ϕ2 −ϕ1)/ε0 (4) (ϕ1 + ϕ2)ε0

Q41.A thin spherical conducting shell of radius R has a charge q. Another charge Q is placed at the centre of the shell. The electrostatic potential at a point P a distance R2 from the centre of the shell is (1) 2Q (2) 2Q − 2q 4πε0R 4πε0R 4πε0R (3) 2Q + q (4) (q+Q)2 4πε0R 4πε0R 4πε0R