Practice Questions

Q8. For a specific wavelength 670 nm of light coming from a galaxy moving with velocity v, the observed wavelength is 670. 7 nm. The value of v is (1) 3 × 108 m s−1 (2) 3. 13 × 105 m s−1 (3) 3 × 1010 m s−1 (4) 4. 48 × 105 m s−1

Q8. A Carnot engine takes 5000 kcal of heat from a reservoir at 727°C and gives heat to a sink at 127°C. The work done by the engine is (1) 3 × 106J (2) Zero (3) 8. 4 × 106 J (4) 12. 6 × 106 J

Q8. The escape velocity of a body on a planet A is 12 km s−1 . The escape velocity of the body on another planet B, whose density is four times and radius is half of the planet A , is (1) 12 km s−1 (2) 24 km s−1 (3) 36 km s−1 (4) 6 km s−1

Q8. Two metallic plates form a parallel plate capacitor. The distance between the plate is '𝑑'. A metal sheet of 𝑑 thickness and of area equal to area of each plate is introduced between the plates. What will be the ratio of the 2 JEE Main 2022 (25 Jun Shift 2) JEE Main Previous Year Paper new capacitance to the original capacitance of the capacitor? (1) 1: 2 (2) 2: 1 (3) 1: 4 (4) 4: 1

Q8. Read the following statements : A . When small temperature difference between a liquid and its surrounding is doubled the rate of loss of heat of the liquid becomes twice. B. Two bodies P and Q having equal surface areas are maintained at temperature 10°C and 20°C . The thermal radiation emitted in a given time by P and Q are in the ratio 1 : 1. 15 C. A carnot Engine working between 100 K and 400 K has an efficiency of 75% D. When small temperature difference between a liquid and its surrounding is quadrupled, the rate of loss of heat of the liquid becomes twice. Choose the correct answer from the options given below : (1) A, B, C only (2) A, B only (3) A, C only (4) B, C, D only

Q8. A vessel contains 14 g of nitrogen gas at a temperature of 27°C. The amount of heat to be transferred to the gas to double the r.m.s. speed of its molecules will be : (Take R = 8. 32 J mol−1 k−1 ) (1) 2229 J (2) 5616 J (3) 9360 J (4) 13, 104 J

Q8. Resistance of the wire is measured as 2 Ω and 3 Ω at 10°C and 30°C respectively. Temperature coefficient of resistance of the material of the wire is (1) 0. 033∘C−1 (2) −0. 033∘C−1 (3) 0. 011∘C−1 (4) 0. 055°C−1

Q8. A thermodynamic system is taken from an original state 𝐷 to an intermediate state 𝐸 by the linear process shown in the figure. Its volume is then reduced to the original volume from 𝐸 to 𝐹 by an isobaric process. The total work done by the gas from 𝐷 to 𝐸 to 𝐹 will be (1) -450 J (2) 450 J (3) 900 J (4) 1350 J

Q8. The velocity of a small ball of mass m and density d1 , when dropped in a container filled with glycerine, becomes constant after some time. If the density of glycerine is d2 , then the viscous force acting on the ball, will be (1) mg(1 −d1d2 ) (2) mg(1 −d2d1 ) (3) mg( d1d2 −1) (4) mg( d2d1 −1)

Q8. In 1stmsup case, Carnot engine operates between temperatures 300 K and 100 K . In 2ndmsup case, as shown in the figure, a combination of two engines is used. The efficiency of this combination (in 2ndmsup case) will be : JEE Main 2022 (27 Jul Shift 2) JEE Main Previous Year Paper (1) same as the 1st case (2) always greater than the 1st case (3) always less than the 1st case (4) may increase or decrease with respect to the 1st case

Q8. A lead bullet penetrates into a solid object and melts. Assuming that 40% of its kinetic energy is used to heat it, the initial speed of bullet is (Given, initial temperature of the bullet = 127°C, Melting point of the bullet = 327°C, Latent heat of fusion of lead = 2. 5 × 104 J kg−1 , Specific heat capacity of lead = 125 J kg K−1 ) (1) 125 m s−1 (2) 500 m s−1 (3) 250 m s−1 (4) 600 m s−1

Q8. Given below are two statements: Statement I :The average momentum of a molecule in a sample of an ideal gas depends on temperature. JEE Main 2022 (28 Jul Shift 1) JEE Main Previous Year Paper Statement II : The rms speed of oxygen molecules in a gas is 𝑣. If the temperature is doubled and the oxygen molecules dissociate into oxygen atoms, the rms speed will become 2𝑣. In the light of the above statements, choose the correct answer from the options given below : (1) Both Statement I and Statement II are true (2) Both Statement I and Statement II are false (3) Statement I is true but Statement II is false (4) Statement I is false but Statement II is true 2𝜋

Q8. Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Clothes containing oil or grease stains cannot be cleaned by water wash. Reason (R) : Because the angle of contact between the oil/ grease and water is obtuse. In the light of the above statements, choose the correct answer from the option given below. (1) Both (A) and (R) are true and (R) is the correct (2) Both (A) and (R) are true but (R) is not the explanation of (A) correct explanation of (A) (3) (A) is true but (R) is false (4) (A) is true but (R) is true

Q8. A thermally insulated vessel contains an ideal gas of molecular mass M and ratio of specific heats 1. 4. Vessel is moving with speed v and is suddenly brought to rest. Assuming no heat is lost to the surrounding and vessel temperature of the gas increases by : ( R = universal gas constant) (1) Mv2 (2) Mv2 7R 5R (3) 2 Mv27R (4) 7 Mv25R

Q8. A gas has 𝑛 degrees of freedom. The ratio of specific heat of gas at constant volume to the specific heat of gas at constant pressure will be 𝑛 𝑛+ 2 (1) (2) 𝑛+ 2 𝑛 (3) 𝑛 (4) 𝑛 2𝑛+ 2 𝑛- 2

Q9. A mixture of hydrogen and oxygen has volume 2000 cm3 , temperature 300 K, pressure 100 kPa and mass 0. 76 g . The ratio of number of moles of hydrogen to number of moles of oxygen in the mixture will be [Take gas constant R = 8. 3 J K−1 mol−1 ] (1) 1 (2) 3 3 1 (3) 1 (4) 16 16 1

Q9. A Carnot engine whose heat sinks at 27°C, has an efficiency of 25%. By how many degrees should the temperature of the source be changed to increase the efficiency by 100% of the original efficiency ? (1) Increases by 18°C (2) Increases by 200°C (3) Increases by 120°C (4) Increases by 73°C

Q9. In figure (A), mass 2𝑚 is fixed on mass 𝑚 which is attached to two springs of spring constant 𝑘. In figure (B), mass 𝑚 is attached to two spring of spring constant 𝑘 and 2𝑘. If mass 𝑚 in (A) and (B) are displaced by distance 𝑥 horizontally and then released, then time period 𝑇1 and 𝑇2 corresponding to (A) and (B) respectively follow the relation. 𝑇1 3 𝑇1 3 (1) (2) = √2 𝑇2 = √ 2 𝑇2 2 √2 (3) 𝑇1 (4) 𝑇1 = = √ 3 3 𝑇2 𝑇2

Q9. A wire of length L is hanging from a fixed support. The length changes to L1 and L2 when masses 1 kg and 2 kg are suspended respectively from its free end. Then the value of L is equal to (1) √L1 L2 (2) L1+L22 (3) 2L1 −L2 (4) 3L1 −L2

Q9. The velocity of sound in a gas, in which two wavelengths 4. 08 m and 4. 16 m produce 40 beats in 12 s , will be (1) 282. 8 m s−1 (2) 175. 5 m s−1 (3) 353. 6 m s−1 (4) 707. 2 m s−1

Q9. A teacher in his physics laboratory allotted an experiment to determine the resistance 𝐺 a galvanometer. 1 Students took the observations for deflection in the galvanometer. Which of the below is true for measuring 3 value of 𝐺? (1) 1 deflection method cannot be used for (2) 1 deflection method can be used and in this case 3 3 determining the resistance of the galvanometer. the 𝐺 equals to twice the value of shunt resistance(s). 1 1 (3) deflection method can be used and in this case, (4) deflection method can be used and in this case 3 3 the G equals to three times the value of shunt the 𝐺 value equals to the shunt resistance(s) resistance(s).

Q9. Time period of a simple pendulum in a stationary lift is T . If the lift accelerates with g vertically upwards then 6 the time period will be (Where g = acceleration due to gravity) (1) (2) T T √65 √56 (3) (4) T T √67 √76

Q9. Two massless springs with spring constants 2k and 9k, carry 50 g and 100 g masses at their free ends. These two masses oscillate vertically such that their maximum velocities are equal. Then, the ratio of their respective JEE Main 2022 (24 Jun Shift 2) JEE Main Previous Year Paper amplitudes will be : (1) 3 : 2 (2) 1 : 2 (3) 3 : 1 (4) 2 : 3

Q9. A vessel contains 16 g of hydrogen and 128 g of oxygen at standard temperature and pressure. The volume of the vessel in cm3 is : (1) 72 × 105 (2) 32 × 105 (3) 27 × 104 (4) 54 × 104

Q9. Same gas is filled in two vessels of the same volume at the same temperature. If the ratio of the number of molecules is 1 : 4, then A . The r.m.s. velocity of gas molecules in two vessels will be the same. B. The ratio of pressure in these vessels will be 1 : 4 . C. The ratio of pressure will be 1 : 1 . D. The r.m.s. velocity of gas molecules in two vessels will be in the ratio of 1 : 4 . (1) A and C only (2) B and D only (3) A and B only (4) C and D only