Practice Questions

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. 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. 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. 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. 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 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. 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 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

Q8. Starting with the same initial conditions, an ideal gas expands from volume V1 to V2 in three different ways. The work done by the gas is W1 if the process is purely isothermal, W2 , if the process is purely adiabatic and W3 if the process is purely isobaric. Then, choose the correct option (1) W2 < W1 < W3 (2) W1 < W2 < W3 (3) W2 < W3 < W1 (4) W3 < W1 < W2

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. 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 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. 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. Following statements are given (1) The average kinetic energy of a gas molecule decreases when the temperature is reduced. (2) The average kinetic energy of a gas molecule increases with increase in pressure at constant temperature. (3) The average kinetic energy of a gas molecule decreases with increases in volume. (4) Pressure of a gas increases with increase in temperature at constant volume. (5) The volume of gas decreases with increase in temperature. Choose the correct answer from the options given below : (1) (1) and (4) only (2) (1), (2) and (4) only (3) (2) and (4) only (4) (1), (2) and (5) only

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. Which statements are correct about degrees of freedom? A. A molecule with n degrees of freedom has n2 different ways of storing energy. B. Each degree of freedom is associated with 1 RT average energy per mole. 2 C. A monoatomic gas molecule has 1 rotational degree of freedom where as diatomic molecule has 2 rotational degrees of freedom D. CH4 has a total to 6 degrees of freedom. Choose the correct answer from the option given below: (1) B and C only (2) B and D only (3) A and B only (4) C and D only

Q9. A transverse wave is represented by 𝑦= 2sin𝜔𝑡- 𝑘𝑥cm. The value of wavelength (in cm) for which the wave velocity becomes equal to the maximum particle velocity, will be (1) 4𝜋 (2) 2𝜋 (3) 𝜋 (4) 2

Q9. Sixty four conducting drops each of radius 0. 02 m and each carrying a charge of 5 μC are combined to form a bigger drop. The ratio of surface density of bigger drop to the smaller drop will be (1) 1 : 4 (2) 4 : 1 (3) 1 : 8 (4) 8 : 1

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

Q9. Two metallic wires of identical dimensions are connected is series. If σ1 and σ2 are the conductivities of the these wires respectively, the effective conductivity of the combination is : (1) σ1σ2 (2) 2σ1σ2 σ1+σ2 σ1+σ2 (3) σ1+σ2 (4) σ1+σ2 2σ1σ2 σ1σ2

Q9. Let η1 is the efficiency of an engine at T1 = 447°C and T2 = 147°C while η2 is the efficiency at T1 = 947°C and T2 = 47°C. The ratio η2η1 will be (1) 0. 41 (2) 0. 56 (3) 0. 73 (4) 0. 70

Q9. A sample of an ideal gas is taken through the cyclic process ABCA as shown in figure. It absorbs, 40 J of heat during the part AB, no heat during BC and rejects 60 J of heat during CA. A work of 50 J is done on the gas during the part BC . The internal energy of the gas at A is 1560 J. The work done by the gas during the part CA is (1) 20 J (2) 30 J (3) −30 J (4) −60 J

Q9. The root mean square speed of smoke particles of mass 5 × 10-17 kg in their Brownian motion in air at NTP is approximately. [Given 𝑘= 1 . 38 × 10-23J K-1] (1) 60 mm s-1 (2) 12 mm s-1 (3) 15 mm s-1 (4) 36 mm s-1

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