Physics Syllabus (JEE Main)
Q. If the RMS speed of a gas is 400 m/s at 300 K, what will be the RMS speed at 600 K?
A.
400 m/s
B.
800 m/s
C.
400√2 m/s
D.
800√2 m/s
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Solution
The RMS speed increases with the square root of the temperature. Therefore, at 600 K, the RMS speed will be 400 * sqrt(2), which is approximately 800 m/s.
Correct Answer: B — 800 m/s
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Q. If the RMS speed of a gas is 400 m/s, what is the kinetic energy per molecule at 300 K?
A.
0.5 mJ
B.
0.4 mJ
C.
0.2 mJ
D.
0.1 mJ
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Solution
Kinetic energy per molecule = (1/2)mv^2. Using v = 400 m/s and m = M/N_A, we find KE = 0.5 mJ.
Correct Answer: A — 0.5 mJ
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Q. If the RMS speed of a gas is 400 m/s, what is the speed of the gas molecules in terms of average speed?
A.
400 m/s
B.
300 m/s
C.
500 m/s
D.
600 m/s
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Solution
The average speed is related to RMS speed by the relation v_avg = (2/3) * v_rms. Thus, v_avg = (2/3) * 400 = 267 m/s.
Correct Answer: B — 300 m/s
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Q. If the RMS speed of a gas is 400 m/s, what is the speed of the molecules in terms of average speed?
A.
400 m/s
B.
300 m/s
C.
500 m/s
D.
600 m/s
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Solution
The average speed of gas molecules is approximately 0.8 times the RMS speed, so average speed = 0.8 * 400 m/s = 320 m/s.
Correct Answer: B — 300 m/s
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Q. If the RMS speed of a gas is 500 m/s, what is the speed of the gas molecules at 1/2 of the RMS speed?
A.
250 m/s
B.
500 m/s
C.
1000 m/s
D.
125 m/s
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Solution
The speed at 1/2 of the RMS speed is simply 500 m/s / 2 = 250 m/s.
Correct Answer: A — 250 m/s
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Q. If the RMS speed of a gas is 500 m/s, what is the speed of the gas molecules in terms of average speed?
A.
500 m/s
B.
250 m/s
C.
400 m/s
D.
600 m/s
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Solution
The average speed of gas molecules is related to the RMS speed by the relation v_avg = (v_rms * sqrt(8/3)). Therefore, the average speed is approximately 400 m/s.
Correct Answer: C — 400 m/s
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Q. If the RMS speed of a gas is 500 m/s, what is the speed of the molecules in the gas?
A.
500 m/s
B.
250 m/s
C.
1000 m/s
D.
It varies
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Solution
The RMS speed is an average measure; individual molecular speeds will vary around this value.
Correct Answer: D — It varies
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Q. If the RMS speed of a gas is 500 m/s, what is the temperature if the molar mass is 0.028 kg/mol?
A.
200 K
B.
300 K
C.
400 K
D.
500 K
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Solution
Using v_rms = sqrt(3RT/M), we rearrange to find T = (v_rms^2 * M) / (3R). Plugging in values gives T approximately 300 K.
Correct Answer: B — 300 K
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Q. If the slit width is equal to the wavelength of light used, what is the expected diffraction pattern?
A.
No diffraction
B.
Single maximum
C.
Wide central maximum
D.
Narrow central maximum
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Solution
When the slit width is equal to the wavelength, a wide central maximum is observed due to significant diffraction.
Correct Answer: C — Wide central maximum
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Q. If the slit width is halved in a single-slit diffraction experiment, what happens to the width of the central maximum?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
If the slit width is halved, the width of the central maximum doubles, as it is inversely proportional to the slit width.
Correct Answer: A — It doubles
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Q. If the slit width is halved in a single-slit diffraction experiment, what happens to the angular width of the central maximum?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
Halving the slit width increases the angular width of the central maximum, making it double.
Correct Answer: A — It doubles
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Q. If the speed of a wave in a medium is 300 m/s and its wavelength is 3 m, what is the frequency of the wave?
A.
100 Hz
B.
150 Hz
C.
200 Hz
D.
300 Hz
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Solution
Frequency f = v/λ = 300 m/s / 3 m = 100 Hz.
Correct Answer: B — 150 Hz
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Q. If the speed of an object in circular motion is doubled, what happens to the centripetal acceleration?
A.
It remains the same
B.
It doubles
C.
It quadruples
D.
It halves
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Solution
Centripetal acceleration a_c = v²/r. If v is doubled, a_c increases by a factor of 4.
Correct Answer: C — It quadruples
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Q. If the speed of light in vacuum is 3 x 10^8 m/s, what is the speed of light in a medium with a refractive index of 1.5?
A.
2 x 10^8 m/s
B.
2.5 x 10^8 m/s
C.
3 x 10^8 m/s
D.
1.5 x 10^8 m/s
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Solution
Speed of light in medium = c/n = (3 x 10^8 m/s) / 1.5 = 2 x 10^8 m/s.
Correct Answer: A — 2 x 10^8 m/s
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Q. If the strain in a material is 0.01 and the Young's modulus is 150 GPa, what is the stress?
A.
1.5 MPa
B.
15 MPa
C.
150 MPa
D.
1500 MPa
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Solution
Stress = Young's modulus × Strain = 150 GPa × 0.01 = 150 MPa.
Correct Answer: C — 150 MPa
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Q. If the stress applied to a material is doubled, what happens to the strain if the material behaves elastically?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Hooke's Law, if stress is doubled, strain also doubles for elastic materials.
Correct Answer: A — It doubles
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Q. If the supply voltage in a Wheatstone bridge is increased, how does it affect the balance condition?
A.
It does not affect the balance condition
B.
It makes the bridge unbalanced
C.
It increases the current in the circuit
D.
It decreases the resistance
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Solution
Increasing the supply voltage does not affect the balance condition; it remains dependent on the resistance ratios.
Correct Answer: A — It does not affect the balance condition
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Q. If the surface tension of a liquid is 0.072 N/m, what is the force acting on a wire of length 0.5 m placed on the surface of the liquid?
A.
0.036 N
B.
0.072 N
C.
0.144 N
D.
0.5 N
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Solution
Force = Surface Tension × Length = 0.072 N/m × 0.5 m = 0.036 N.
Correct Answer: A — 0.036 N
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Q. If the temperature difference between two bodies is increased, what happens to the rate of heat transfer?
A.
Decreases
B.
Increases
C.
Remains constant
D.
Becomes zero
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Solution
According to Newton's law of cooling, the rate of heat transfer increases with an increase in temperature difference.
Correct Answer: B — Increases
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Q. If the temperature is recorded as 30°C with an error of 0.5°C, what is the maximum possible temperature?
A.
30.5°C
B.
29.5°C
C.
31°C
D.
30°C
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Solution
Maximum possible temperature = Measured value + Error = 30 + 0.5 = 30.5°C
Correct Answer: A — 30.5°C
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Q. If the temperature of a conductor increases, what happens to its resistivity?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Depends on the material
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Solution
For most conductors, resistivity increases with temperature due to increased atomic vibrations.
Correct Answer: A — Increases
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Q. If the temperature of a gas is doubled at constant volume, what happens to the pressure?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Gay-Lussac's Law, if the temperature of a gas is increased while keeping the volume constant, the pressure will also increase proportionally, thus it doubles.
Correct Answer: A — It doubles
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Q. If the temperature of a gas is doubled, how does its RMS speed change?
A.
Increases by a factor of sqrt(2)
B.
Increases by a factor of 2
C.
Increases by a factor of 4
D.
Remains the same
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Solution
The RMS speed is proportional to the square root of the temperature. If the temperature is doubled, the RMS speed increases by a factor of sqrt(2).
Correct Answer: A — Increases by a factor of sqrt(2)
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Q. If the temperature of a gas is doubled, what happens to its RMS speed?
A.
Increases by a factor of sqrt(2)
B.
Increases by a factor of 2
C.
Increases by a factor of sqrt(3)
D.
Remains the same
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Solution
The RMS speed is proportional to the square root of the temperature. If the temperature is doubled, the RMS speed increases by a factor of sqrt(2).
Correct Answer: A — Increases by a factor of sqrt(2)
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Q. If the temperature of a gas is halved, what happens to its RMS speed?
A.
Increases by sqrt(2)
B.
Decreases by sqrt(2)
C.
Remains the same
D.
Decreases by 2
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Solution
RMS speed is directly proportional to the square root of temperature. Halving the temperature results in a decrease in RMS speed by sqrt(2).
Correct Answer: B — Decreases by sqrt(2)
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Q. If the temperature of a gas is increased at constant volume, what happens to the pressure?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes zero
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Solution
According to Gay-Lussac's Law, if the temperature of a gas increases at constant volume, the pressure increases.
Correct Answer: A — Increases
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Q. If the temperature of a gas is increased from 200 K to 800 K, how does the RMS speed change?
A.
Increases by 2
B.
Increases by 4
C.
Increases by sqrt(4)
D.
Decreases by sqrt(4)
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Solution
RMS speed increases by sqrt(4) = 2, since v_rms is proportional to sqrt(T).
Correct Answer: C — Increases by sqrt(4)
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Q. If the temperature of a gas is increased from 300 K to 600 K, how does the RMS speed change?
A.
It doubles
B.
It increases by sqrt(2)
C.
It increases by sqrt(3)
D.
It remains the same
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Solution
RMS speed is proportional to the square root of temperature. Increasing from 300 K to 600 K increases the speed by sqrt(2).
Correct Answer: B — It increases by sqrt(2)
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Q. If the temperature of a gas is increased while keeping the volume constant, what happens to the pressure?
A.
Pressure decreases
B.
Pressure increases
C.
Pressure remains constant
D.
Pressure becomes zero
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Solution
According to Gay-Lussac's Law, if the temperature of a gas is increased while keeping the volume constant, the pressure increases.
Correct Answer: B — Pressure increases
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Q. If the temperature of a liquid increases, what happens to its viscosity?
A.
Increases
B.
Decreases
C.
Remains constant
D.
Varies unpredictably
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Solution
The viscosity of a liquid generally decreases with an increase in temperature.
Correct Answer: B — Decreases
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