Physics Syllabus (JEE Main)
Q. If the mass of the Earth is 6 × 10^24 kg and its radius is 6.4 × 10^6 m, what is the acceleration due to gravity at its surface?
A.
9.8 m/s²
B.
10 m/s²
C.
9.81 m/s²
D.
8.9 m/s²
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Solution
g = G * M / R² = (6.67 × 10^-11) * (6 × 10^24) / (6.4 × 10^6)² = 9.81 m/s²
Correct Answer: C — 9.81 m/s²
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Q. If the mass of the Earth is M and its radius is R, what is the gravitational acceleration at the surface of the Earth?
A.
g = GM/R^2
B.
g = GMR^2
C.
g = G/MR^2
D.
g = MR/G
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Solution
The gravitational acceleration at the surface of the Earth is given by g = GM/R^2.
Correct Answer: A — g = GM/R^2
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Q. If the mass of the Earth is M and the radius is R, what is the gravitational acceleration at the surface of the Earth?
A.
g = GM/R^2
B.
g = GMR^2
C.
g = G/R
D.
g = M/R^2
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Solution
The gravitational acceleration at the surface of the Earth is given by g = GM/R^2.
Correct Answer: A — g = GM/R^2
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Q. If the mass of the Earth is M and the radius is R, what is the gravitational force acting on a satellite of mass m at a height h?
A.
GmM/R^2
B.
GmM/(R+h)^2
C.
GmM/(R-h)^2
D.
GmM/h^2
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Solution
The gravitational force F acting on a satellite at height h is given by F = GmM/(R+h)^2, where G is the gravitational constant.
Correct Answer: B — GmM/(R+h)^2
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Q. If the mass of the Earth were to double while its radius remained the same, what would happen to the gravitational acceleration at its surface?
A.
It would double
B.
It would remain the same
C.
It would halve
D.
It would increase by a factor of four
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Solution
Gravitational acceleration is directly proportional to mass, so if the mass doubles, g also doubles.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to double while its radius remains the same, what would happen to the gravitational acceleration at its surface?
A.
It would double
B.
It would remain the same
C.
It would halve
D.
It would increase by a factor of four
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Solution
Gravitational acceleration is directly proportional to mass; thus, if the mass doubles, g also doubles.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to double while the radius remains the same, what would happen to the weight of an object on its surface?
A.
It would double
B.
It would remain the same
C.
It would increase by a factor of four
D.
It would decrease by half
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Solution
Weight is proportional to mass; thus, if the Earth's mass doubles, the weight of an object on its surface also doubles.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to double, what would happen to the gravitational force between the Earth and an object on its surface?
A.
It would double
B.
It would remain the same
C.
It would halve
D.
It would quadruple
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Solution
F ∝ M; if M doubles, F also doubles.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to double, what would happen to the gravitational force between two objects on its surface?
A.
It would double
B.
It would remain the same
C.
It would be halved
D.
It would quadruple
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Solution
F = G * (m1 * m2) / r², doubling the mass of Earth doubles the force.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to double, what would happen to the gravitational force it exerts on an object at its surface?
A.
It would double
B.
It would remain the same
C.
It would increase by a factor of four
D.
It would decrease by half
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Solution
If the mass of the Earth doubles, the gravitational force on an object at its surface would also double.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to double, what would happen to the weight of an object on its surface?
A.
It would double
B.
It would remain the same
C.
It would be halved
D.
It would be quartered
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Solution
Weight is directly proportional to mass. If the Earth's mass doubles, the weight of the object also doubles.
Correct Answer: A — It would double
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Q. If the mass of the Earth were to increase while the radius remains constant, what would happen to the gravitational force experienced by an object on its surface?
A.
It would decrease
B.
It would increase
C.
It would remain the same
D.
It would become zero
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Solution
If the mass of the Earth increases, the gravitational force experienced by an object on its surface would increase.
Correct Answer: B — It would increase
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Q. If the measured length of a rod is 20 cm with an error of 0.5 cm, what is the relative error in the measurement?
A.
0.025
B.
0.05
C.
0.0025
D.
0.005
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Solution
Relative error = (Absolute error / Measured value) = 0.5 / 20 = 0.025 or 2.5%
Correct Answer: B — 0.05
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Q. If the measured value of a quantity is 100 with a relative error of 0.02, what is the absolute error?
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Solution
Absolute error = Relative error * Measured value = 0.02 * 100 = 2.
Correct Answer: A — 2
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Q. If the measured value of a quantity is 75 with a relative error of 0.04, what is the true value?
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Solution
Relative error = Absolute error / True value. Let true value be x. 0.04 = |75 - x| / x. Solving gives x = 78.
Correct Answer: B — 78
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Q. If the molar mass of a gas is doubled, how does its RMS speed change?
A.
Increases by sqrt(2)
B.
Decreases by sqrt(2)
C.
Remains the same
D.
Increases by 2
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Solution
RMS speed is inversely proportional to the square root of molar mass, so if M is doubled, v_rms decreases by sqrt(2).
Correct Answer: B — Decreases by sqrt(2)
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Q. If the molar mass of a gas is doubled, how does the RMS speed change?
A.
Increases by sqrt(2)
B.
Decreases by sqrt(2)
C.
Remains the same
D.
Increases by 2
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Solution
The RMS speed is inversely proportional to the square root of the molar mass. If M is doubled, v_rms decreases by sqrt(2).
Correct Answer: B — Decreases by sqrt(2)
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Q. If the molar mass of a gas is halved, what happens to its RMS speed?
A.
Increases by a factor of sqrt(2)
B.
Increases by a factor of 2
C.
Decreases by a factor of sqrt(2)
D.
Remains the same
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Solution
If the molar mass is halved, the RMS speed increases by a factor of sqrt(2) because RMS speed is inversely proportional to the square root of molar mass.
Correct Answer: A — Increases by a factor of sqrt(2)
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Q. If the moment of inertia of a body is 10 kg m², what is the angular momentum when it rotates with an angular velocity of 5 rad/s?
A.
50 kg m²/s
B.
10 kg m²/s
C.
5 kg m²/s
D.
2 kg m²/s
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Solution
Angular momentum L = Iω = 10 kg m² * 5 rad/s = 50 kg m²/s.
Correct Answer: A — 50 kg m²/s
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Q. If the moment of inertia of a body is 10 kg m², what is the rotational kinetic energy when it rotates with an angular velocity of 5 rad/s?
A.
125 J
B.
50 J
C.
100 J
D.
75 J
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Solution
Rotational kinetic energy is given by KE = 1/2 I ω² = 1/2 * 10 * 5² = 125 J.
Correct Answer: A — 125 J
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Q. If the moment of inertia of a body is 10 kg·m² and it is subjected to a torque of 20 N·m, what is the angular acceleration?
A.
2 rad/s²
B.
0.5 rad/s²
C.
5 rad/s²
D.
10 rad/s²
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Solution
Using τ = Iα, we have α = τ/I = 20 N·m / 10 kg·m² = 2 rad/s².
Correct Answer: A — 2 rad/s²
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Q. If the moment of inertia of a body is doubled, what happens to its rotational kinetic energy if the angular velocity remains constant?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
Rotational kinetic energy is given by KE = 1/2 I ω^2. If I is doubled and ω remains constant, KE also doubles.
Correct Answer: A — Doubles
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Q. If the moment of inertia of a body is doubled, what will be the effect on its angular acceleration if the torque applied remains constant?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Increases by a factor of four
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Solution
Angular acceleration α = τ/I. If I is doubled and τ remains constant, α is halved.
Correct Answer: B — Halves
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Q. If the moment of inertia of a body is doubled, what will happen to its angular momentum if the angular velocity remains constant?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
Angular momentum L = Iω; if I is doubled and ω remains constant, L also doubles.
Correct Answer: A — Doubles
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Q. If the moment of inertia of a body is increased, what happens to its angular acceleration for a constant torque?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
According to Newton's second law for rotation, τ = Iα, if I increases and τ is constant, α must decrease.
Correct Answer: B — Decreases
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Q. If the natural frequency of a damped oscillator is 5 rad/s and the damping ratio is 0.2, what is the damped frequency?
A.
4.8 rad/s
B.
5 rad/s
C.
5.2 rad/s
D.
5.5 rad/s
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Solution
Damped frequency (ω_d) = ω_n√(1-ζ^2) = 5√(1-0.2^2) = 5√(0.96) ≈ 4.8 rad/s.
Correct Answer: A — 4.8 rad/s
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Q. If the object distance is equal to the focal length of a convex lens, what is the nature of the image formed?
A.
Real and inverted
B.
Virtual and upright
C.
At infinity
D.
No image formed
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Solution
When the object distance equals the focal length, the image is formed at infinity.
Correct Answer: C — At infinity
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Q. If the object distance is equal to the focal length of a convex lens, what type of image is formed?
A.
Real and inverted
B.
Virtual and upright
C.
At infinity
D.
No image formed
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Solution
When the object is at the focal length, the image is formed at infinity.
Correct Answer: C — At infinity
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Q. If the peak current in an AC circuit is 5 A, what is the average current over one complete cycle?
A.
5 A
B.
2.5 A
C.
0 A
D.
7.07 A
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Solution
The average current over one complete cycle is I_avg = I_peak/√2 = 5/√2 = 2.5 A.
Correct Answer: B — 2.5 A
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Q. If the peak voltage of an AC source is 200 V, what is the RMS voltage?
A.
100 V
B.
141.42 V
C.
200 V
D.
282.84 V
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Solution
The RMS voltage (V_rms) is given by V_rms = V_peak / √2. Therefore, V_rms = 200 V / √2 = 141.42 V.
Correct Answer: B — 141.42 V
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