Practice Questions

Q40.Given below are two statements. One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : The binding energy per nucleon is found to be practically independent of the atomic number A, for nuclei with mass numbers between 30 and 170. Reason (R): Nuclear force is long range. In the light of the above statements, choose the correct answer from the options given below : (1) (A) is true but (R) is false (2) (A) is false but (R) is true (3) Both (A) and (R) are true and (R) is the correct (4) Both (A) and (R) are true but (R) is NOT the explanation of (A) correct explanation of (A)

Q40.The energy E and momentum p of a moving body of mass m are related by some equation. Given that c represents the speed of light, identify the correct equation (1) E2 = pc2 + m2c2 (2) E2 = p2c2 + m2c2 (3) E2 = pc2 + m2c4 (4) E2 = p2c2 + m2c4

Q40.Which one of the following is the correct dimensional formula for the capacitance in F ? M, L, T and C stand for unit of mass, length, time and charge, (1) [F] = [C2M−1 L−2 T2] (2) [F] = [C2M−2 L2 T2] (3) [F] = [CM−2 L−2 T−2] (4) [F] = [CM−1 L−2 T2]

Q40.Find the equivalent resistance between two ends of the following circuit (1) r (2) r 9 3 (3) r (4) r 6

Q40.The work functions of cesium (Cs) and lithium (Li) metals are 1.9 eV and 2.5 eV , respectively. If we incident a light of wavelength 550 nm on these two metal surfaces, then photo-electric effect is possible for the case of (1) Both Cs and Li (2) Neither Cs nor Li (3) Cs only (4) Li only

Q40.A radioactive nucleus n2 has 3 times the decay constant as compared to the decay constant of another radioactive nucleus n1 . If initial number of both nuclei are the same, what is the ratio of number of nuclei of n2 to the number of nuclei of n1 , after one half-life of n1 ? (1) 1/8 (2) 8 (3) 4 (4) 1/4

Q41. A tube of length L is shown in the figure. The radius of cross section at the point (1) is 2 cm and at the point (2) is 1 cm , respectively. If the velocity of water entering at point (1) is 2 m/s, then velocity of water leaving the point (2) will be (1) 4 m/s (2) 2 m/s (3) 6 m/s (4) 8 m/s

Q41.Two spherical bodies of same materials having radii 0.2 m and 0.8 m are placed in same atmosphere. The temperature of the smaller body is 800 K and temperature of the bigger body is 400 K . If the energy radiated from the smaller body is E, the energy radiated from the bigger body is (assume, effect of the surrounding temperature to be negligible), (1) 16 E (2) E (3) 64 E (4) 256 E

Q41.The fractional compression ( ΔVV ) of water at the depth of 2.5 km below the sea level is ______ % . Given, the Bulk modulus of water = 2 × 109 N m−2 , density of water = 103 kgm−3 , acceleration due to gravity = g = 10 m s−2 . (1) 1.25 (2) 1.0 (3) 1.75 (4) 1.5

Q41. Two concave refracting surfaces of equal radii of curvature and refractive index 1.5 face each other in air as shown in figure. A point object O is placed midway, between P and B . The separation between the images of O, formed by each refracting surface is : (1) 0.214 R (2) 0.411 R (3) 0.124 R (4) 0.114 R

Q41.Consider following statements: A. Surface tension arises due to extra energy of the molecules at the interior as compared to the molecules at the surface, of a liquid. B. As the temperature of liquid rises, the coefficient of viscosity increases. C. As the temperature of gas increases, the coefficient of viscosity increases D. The onset of turbulence is determined by Reynold's number. E. In a steady flow two stream lines never intersect. Choose the correct answer from the options given below: 2025 (28 Jan Shift 1) JEE Main Previous Year Paper (1) C, D, E Only (2) A, D, E Only (3) B, C, D Only (4) A, B, C Only

Q41.The temperature of a body in air falls from 40∘C to 24∘C in 4 minutes. The temperature of the air is 16∘C. The temperature of the body in the next 4 minutes will be: (1) 14 3 ∘C (2) 423 ∘C (3) 28 3 ∘C (4) 563 ∘C

Q41.The Young's double slit interference experiment is performed using light consisting of 480 nm and 600 nm wavelengths to form interference patterns. The least number of the bright fringes of 480 nm light that are required for the first coincidence with the bright fringes formed by 600 nm light is (1) 5 (2) 4 (3) 6 (4) 8

Q41.A balloon and its content having mass M is moving up with an acceleration ' a '. The mass that must be released from the content so that the balloon starts moving up with an acceleration ' 3a′ will be (Take ' g ' as acceleration due to gravity) (1) 2Ma (2) 3Ma 3a+g 2a−g (3) 3Ma (4) 2Ma 2a+g 3a−g

Q42.In the diagram given below, there are three lenses formed. Considering negligible thickness of each of them as compared to |R1| and |R2|, i.e., the radii of curvature for upper and lower surfaces of the glass lens, the power of the combination is (1) 1 − + |R2| |R2| 6 ( |R1|1 1 ) (2) −16 ( |R1|1 1 ) (3) 1 + − |R2| |R2| 6 ( |R1|1 1 ) (4) −16 ( |R1|1 1 )

Q42.A circular disk of radius R meter and mass M kg is rotating around the axis perpendicular to the disk. An external torque is applied to the disk such that θ(t) = 5t2 −8t, where θ(t) is the angular position of the rotating disc as a function of time t. How much power is delivered by the applied torque, when t = 2 s ? (1) 72MR2 (2) 8MR2 (3) 108MR2 (4) 60MR2

Q42. A poly-atomic molecule ( CV = 3R, CP = 4R, where R is gas constant) goes from phase space point A (PA = 105 Pa, VA = 4 × 10−6 m3) to point B (PB = 5 × 104 Pa, VB = 6 × 10−6 m3) to point 2025 (29 Jan Shift 2) JEE Main Previous Year Paper C (PC = 104 Pa, VC = 8 × 10−6 m3). A to B is an adiabatic path and B to C is an isothermal path. The net heat absorbed per unit mole by the system is : (1) 500R(ln 3 + ln 4) (2) 450R(ln 4 −ln 3) (3) 500R ln 2 (4) 400R ln 4

Q42.The ratio of vapour densities of two gases at the same temperature is 4 , then the ratio of r.m.s. velocities will 25 be: (1) 25 (2) 2 4 5 (3) 5 (4) 4 2 25

Q42.A parallel plate capacitor was made with two rectangular plates, each with a length of l = 3 cm and breath of b = 1 cm . The distance between the plates is 3μ m . Out of the following, which are the ways to increase the capacitance by a factor of 10 ? A. l = 30 cm, b = 1 cm, d = 1μ m B. l = 3 cm, b = 1 cm, d = 30μ m C. l = 6 cm, b = 5 cm, d = 3μ m D. l = 1 cm, b = 1 cm, d = 10μ m E. l = 5 cm, b = 2 cm, d = 1μ m Choose the correct answer from the options given below: 2025 (24 Jan Shift 1) JEE Main Previous Year Paper (1) A only (2) C only (3) B and D only (4) C and E only

Q42.The center of mass of a thin rectangular plate (fig - x ) with sides of length a and b, whose mass per unit area (σ) varies as σ = σ0xab (where σ0 is a constant), would be (1) ( 23 a, 2b ) (2) ( a2 , 2b ) (3) ( 13 a, 2b ) (4) ( 23 a, 23 b)

Q42.The pair of physical quantities not having same dimensions is : (1) Pressure and Young's modulus (2) Surface tension and impulse (3) Torque and energy (4) Angular momentum and Planck's constant

Q42.A solid sphere is rolling without slipping on a horizontal plane. The ratio of the linear kinetic energy of the centre of mass of the sphere and rotational kinetic energy is : (1) 3 (2) 4 4 3 (3) 5 (4) 2 2 5

Q42.A light source of wavelength λ illuminates a metal surface and electrons are ejected with maximum kinetic energy of 2 eV . If the same surface is illuminated by a light source of wavelength λ , then the maximum 2 kinetic energy of ejected electrons will be (The work function of metal is 1 eV ) (1) 3 eV (2) 2 eV (3) 6 eV (4) 5 eV

Q43.The energy of a system is given as E(t) = α3e−βt , where t is the time and β = 0.3 s−1 . The errors in the measurement of α and t are 1.2% and 1.6% , respectively. At t = 5 s, maximum percentage error in the energy is : (1) 6% (2) 8.4% (3) 11.6% (4) 4%

Q43.Which of the following circuits has the same outpur as that of the given circuit? (1) (2) (3) (4)