Practice Questions

Q8. A machine gun fires a bullet of mass 40 g with a velocity 1200 ms−1 . The man holding it can exert a maximum force of 144 N on the gun. How many bullets can he fire per second at the most? (1) one (2) four (3) two (4) three JEE Main 2004 JEE Main Previous Year Paper

Q10.A block rests on a rough inclined plane making an angle of 30∘ with the horizontal. The coefficient of static friction between the block and the plane is 0.8 . If the frictional force on the block is 10 N , the mass of the block (in kg ) is (take g = 10 m/s2 ) (1) 2.0 (2) 4.0 (3) 1.6 (4) 2.5

Q13.A uniform chain of length 2 m is kept on a table such that a length of 60 cm hangs freely from the edge of the table. The total mass of the chain is 4 kg. What is the work done in pulling the entire chain on the table? (1) 7.2 J (2) 3.6 J (3) 120 J (4) 1200 J

Q15.A body of mass m, accelerates uniformly from rest to v1 in time t1 . The instantaneous power delivered to the body as a function of time t is JEE Main 2004 JEE Main Previous Year Paper (1) mv1t (2) mv21t t1 t21 (3) mv1t2 (4) mv21t t1 t1

Q18.A solid sphere is rotating in free space. If the radius of the sphere is increased keeping mass same which one of the following will not be affected? (1) moment of inertia (2) angular momentum (3) angular velocity (4) rotational kinetic energy.

Q20.A satellite of mass m revolves around the earth of radius R at a height x from its surface. If g is the acceleration due to gravity on the surface of the earth, the orbital speed of the satellite is (1) gx (2) gR R−x (3) g2 (4) gR2 1/2 R+x ( R+x )

Q22.If g is the acceleration due to gravity on the earth's surface, the gain in the potential energy of object of mass m raised from the surface of the earth to a height equal to the radius R of the earth is (1) 2mgR (2) 21 mgR (3) 1 4 mgR (4) mgR

Q25.If two soap bubbles of different radii are connected by a tube, (1) air flows from the bigger bubble to the smaller (2) air flows from bigger bubble to the smaller bubble till the sizes are interchanged. bubble till the sizes are interchanged (3) air flows from the smaller bubble to the bigger. (4) there is no flow of air.

Q26.If the temperature of the sun were to increase from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on earth to what it was previously will be (1) 4 (2) 16 (3) 32 (4) 64

Q27.The temperature of two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively are T2 and T1 (T2 > T1). The rate of heat f equal to transfer through the slab, in a steady state is ( A(T2−T1)Kx )f , with (1) 1 (2) 1/2 (3) 2/3 (4) 1/3

Q28.The thermistors are usually made of (1) metals with low temperature coefficient of (2) metals with high temperature coefficient of resistivity resistivity (3) metal oxides with high temperature coefficient of (4) semiconducting materials having low resistivity " temperature coefficient of resistivity.

Q29.Time taken by a 836 W heater to heat one litre of water from 10∘C to 40∘C is (1) 50 s (2) 100 s (3) 150 s (4) 200 s

Q30.The thermo emf of a thermocouple varies with the temperature θ of the hot junction as E = aθ + bθ2 in volts where the ratio a/b is 700∘C. If the cold junction is kept at 0∘C, then the neutral temperature is (1) 700∘C (2) 350∘C (3) 1400∘C (4) no neutral temperature is possible for this thermocouple. JEE Main 2004 JEE Main Previous Year Paper

Q32.One mole of ideal monoatomic gas (γ = 5/30) is mixed with one mole of diatomic gas (γ = 7/5). What is γ for the mixture? γ denotes the ratio of specific heat at constant pressure, to that at constant volume. (1) 3/2 (2) 23/15 (3) 35/23 (4) 4/3

Q33.Two thermally insulated vessels 1 and 2 are filled with air at temperatures (T1, T2), volume (V1, V2) and pressure (P1, P2) respectively. If the valve joining two vessels is opened, the temperature inside the vessel at equilibrium will be (1) T1 + T2 (2) (T1 + T2)/2 (3) T1 T2(P1 V1+P2 V2) (4) T1 T2(P1 V1+P2 V2) P1 V1 T2+P2 V2 T1 P1 V1 T1+P2 T2 T2

Q34.The bob of a simple pendulum executes simple harmonic motion in water with a period t, while the period of oscillation of the bob is t0 in air. Neglecting frictional force of water and given that the density of the bob is ( 43 ) × 1000 kg/m3 . What relationship between t and t0 is true? (1) t = t0 (2) t = t0/2 (3) t = 2t0 (4) t = 4t0

Q35.A particle at the end of a spring executes simple harmonic motion with a period t1 , while the corresponding period for another spring is t2 . If the period of oscillation with the two springs in series is t, then (1) T = t1 + t2 (2) ∝x2 (3) T−1 = t−11 + t−12 (4) T−2 = t21 + t22

Q37.A particle of mass m is attached to a spring (of spring constant k ) and has a natural angular frequency ω0 . An external force F(t) proportional to cos ωt (ω ≠ω0) is applied to the oscillator. The time displacement of the oscillator will be proportional to (1) m (2) 1 ω20−ω2 m(ω20−ω2) (3) 1 (4) m m(ω20+ω2) ω20+ω2

Q38.In forced oscillation of a particle the amplitude is maximum for a frequency ω1 of the force, while the energy is maximum for a frequency ω2 of the force, then (1) ω1 = ω2 (2) ω1 > ω2 (3) ω1 < ω2 when damping is small and ω1 > ω2 (4) ω1 < ω2 when damping is large

Q40.Two spherical conductor B and C having equal radii and carrying equal charges in them repel each other with a force F when kept apart at some distance. A third spherical conductor having same radius as that of B but uncharged brought in contact with B, then brought in contact with C and finally removed away from both. The new force of repulsion, between B and C is (1) F/4 (2) 3F/4 (3) F/8 (4) 3 F/8 .

Q41.A charged particle q is shot towards another charged particle Q which is fixed, with a speed v it approaches Q upto a closest distance r and then returns. If q were given a speed 2v, the closest distances of approach would be (1) r (2) 2r (3) r/2 (4) r/4

Q44.An α-particle of energy 5MeV is scattered through 180∘ by a fixed uranium nucleus. The distance of the closest approach is of the order of (1) 1Å (2) 10−10 cm (3) 10−12 cm (4) 10−15 cm

Q45. The total current supplied to the circuit by the battery is (1) 1 A (2) 2 A (3) 4A (4) 6 A

Q46.The resistance of the series combination of two resistances is S . When they are joined in parallel through total resistance is P . If S = nP , then the minimum possible value of n is JEE Main 2004 JEE Main Previous Year Paper (1) 4 (2) 3 (3) 2 (4) 1

Q47.An electric current is passed through a circuit containing two wires of the same material, connected in parallel. If the length and radii of the wires are in the ratio of 4/3 and 2/3 , then the ratio of the currents passing through the wire will be (1) 3 (2) 1/3 (3) 8/9 (4) 2