Practice Questions

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

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

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

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

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

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

Q42.Three charges −q1, +q2 and −q3 are placed as shown in the figure. The x-component of the force on −q1 is proportional to (1) q2 −q3 cos θ (2) q2 + q3 sin θ b2 a2 b2 a2 (3) q2 + q3 cos θ (4) q2 −q3 sin θ b2 a2 b2 a2

Q44.The work done in placing a charge of 8 × 10−18 coulomb on a condenser of capacity 100 micro-farad is (1) 16 × 10−32 joule (2) 3.1 × 10−26 joule (3) 4 × 10−10 joule (4) 32 × 10−32 joule

Q45.The length of a wire of a potentiometer is 100 cm, and the e.m.f. of its standard cell is E volt. It is employed to measure the e.m.f of a battery whose internal resistance is 0.5Ω. If the balance point is obtained at l = 30 cm from the positive end, the e.m.f. of the battery is (1) 30E (2) 30E 100.5 (100−0.5) (3) 30(E−0.5i) , where i is the current in the (4) 30E100 100 potentiometer wire

Q47.The thermo e.m.f. of a thermo-couple is 25μV/∘C at room temperature. A galvanometer of 40 ohm resistance, capable of detecting current as low as 10−5 A, is connected with the thermo couple. The smallest temperature JEE Main 2003 JEE Main Previous Year Paper difference that can be detected by this sytem is (1) 16∘C (2) 12∘C (3) 80C (4) 20∘C

Q49.An ammeter reads up to 1 ampere. Its internal resistance is 0.81ohm. To increase the range to 10 A the value of the required shunt is (1) 0.03Ω (2) 0.3Ω (3) 0.9Ω (4) 0.09Ω

Q50.A 3 volt battery with negligible internal resistance is connected in a circuit as shown in the figure. The current I, in the circuit will be (1) 1 A (2) 1.5 A (3) 2 A (4) 1/3 A

Q51.A 220 volt, 1000 watt bulb is connected across a 110 volt mains supply. The power consumed will be (1) 750watt (2) 500watt (3) 250watt (4) 1000watt

Q52.The length of a given cylindrical wire is increased by 100%. Due to the consequent decrease in diameter the change in the resistance of the wire will be (1) 200% (2) 100% (3) 50% (4) 300%

Q53.A thin rectangular magnet suspended freely has a period of oscillation equal to T . Now it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is T ′ , the ratio TT ′ is (1) 1 (2) 1 2√2 2 (3) 2 (4) 1 4

Q54.A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through 60∘ . The torque needed to maintain the needle in this position will be (1) √3 W (2) W (3) √3 2 W (4) 2 W JEE Main 2003 JEE Main Previous Year Paper

Q58.A particle of charge −16 × 10−18 coulomb moving with velocity 10 ms−1 along the x-axis enters a region where a magnetic field of induction B is along the y-axis, and an electric field of magnitude 104 V/m is along the negative z-axis. If the charged particle continues moving along the x-axis, the magnitude of B is (1) 103 Wb/m2 (2) 105 Wb/m2 (3) 1016 Wb/m2 (4) 10−3 Wb/m2