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Physics NEET MCQ
Quiz 1
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Q.1
Which is of the following statement is true Statement A: Gravitational constant G value does not depend on the medium between the bodies Statement B: Gravitational constant G depends on the masses of the bodies and the sizes of the bodies
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A & B both are correct
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only A is correct
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Only B is correct
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A and B both are wrong
Explanation
The gravitational constant G is a genuinely universal constant — it doesn't depend on the medium between the bodies, and it doesn't depend on the masses or sizes of the specific bodies involved either (it's the same G for any two masses anywhere). So Statement A is true, and Statement B is false.
Q.2
If the distance between the earth and sun were half its present value, the number of days in a year would be
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64.5
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129
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182.5
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730
Explanation
By Kepler's third law, T² ∝ r³. Halving the orbital radius (r → r/2): T'² = T² × (1/2)³ = T²/8 → T' = T/√8 T' = 365/(2√2) ≈ 365/2.828 ≈ 129 days.
Q.3
if both the mass of earth and its radius are decreased by 1%,the value of acceleration of gravity will
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Decrease by 1%
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Increase by 1%
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Increase by 2%
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remain unchanged
Explanation
g = GM/R². Using small-percentage (differential) approximation: Δg/g ≈ ΔM/M − 2(ΔR/R) = (−1%) − 2(−1%) = −1% + 2% = +1%. So g increases by about 1%.
Q.4
A body weigh W newton of the surface of the earth. Its weight at a height equal to half the radius of the earth will be
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W/2
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2W/3
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4W/9
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W/4
Explanation
g at height h = g × R²/(R+h)². With h = R/2: g_h = g × R² / (R + R/2)² = g × R² / (3R/2)² = g × R²/(9R²/4) = g × 4/9. Weight at that height = W × 4/9 = 4W/9.
Q.5
Assertion: Angular speed of a planet around the sun increases, when it is closer to the sun. Reason: Total angular momentum of the system remains constant. Choose the correct one
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Both assertion and reason are true and reason is the correct explanation of the assertion
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Both assertion and reason are true but reason is not correct explanation of the assertion
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Assertion is true, but reason is false
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Both assertion and reason are false
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Reason is true but assertion is false.
Explanation
For a planet under the Sun's gravity (a central force), angular momentum L = mr²ω is conserved. As the planet gets closer to the Sun (r decreases), ω must increase to keep L constant — this is exactly Kepler's second law (equal areas in equal times) at work, and it directly explains the increase in angular speed.
Q.6
when a stone of mass m is falling in the earth of mass M, the acceleration of the earth will be
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zero
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mg/M
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Mg/m
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g
Explanation
By Newton's third law, the force the stone exerts on the Earth equals (in magnitude) the force gravity exerts on the stone, which is mg. The Earth's acceleration is then this force divided by Earth's mass: a = mg/M.
Q.7
The weight of the object will be ( More than one correct answer)
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zero at the center of the earth
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same in all the satellites
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same at all the points on the surface of the earthcorrect
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none of the above
Explanation
This question notes "(more than one correct)". At the very centre of the Earth, gravitational pulls from every direction cancel out exactly, so g = 0 there, meaning weight is zero. For an idealised uniform, non-rotating spherical Earth, g also works out the same at every point on the surface (same distance from the centre everywhere), so weight would be the same at all surface points too.
Q.8
Which is of the following statement is true Statement A: it is possible to put an artificial satellite in an orbit such a way that it will remain always directly over New Delhi Statement B: An earth satellite continues to move in the orbit due to centripetal force provided by the burning of the fuel of its engine
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A & B both are correct
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only A is correct
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Only B is correct
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A and B both are wrong
Explanation
A satellite can only stay fixed above one ground point (geostationary) if its orbit is directly above the equator — New Delhi isn't on the equator, so no orbit can keep a satellite permanently overhead there, making Statement A false. And once in orbit, a satellite is held in its path by gravity providing the centripetal force, not by continuously burning engine fuel (engines are only used occasionally for orbit corrections) — making Statement B false too.
Q.9
A mass m is divided into two part ym and (1-y)m .For a given separation, the value of y for which the gravitational attraction between the two pieces becomes maximum
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1/2
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3/5
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1
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2
Explanation
Gravitational attraction between the two pieces: F = G(ym)((1−y)m)/r² ∝ y(1−y). Maximising y(1−y): d/dy[y − y²] = 1 − 2y = 0 → y = 1/2.
Q.10
Two bodies of mass M and 2M are at rest at infinite separation. They move towards each other under the mutual gravitational attraction. Then at separation r ,which of the following is false
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The total energy of the system is not zero
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The force between them is zero
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The center of the mass of the system is moving
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none of the above
Explanation
Starting from rest at infinite separation, both the initial kinetic energy and initial potential energy are zero, so the system's total mechanical energy is exactly zero throughout (energy conservation, no external forces) — and since only an internal, mutual force acts (no external force on the two-body system), the centre of mass must remain exactly where it started, at rest. So the claim that the centre of mass is moving is the false one.
Q.11
The change in the graviational potential energy when a body of mass m is raised to a height nR above the surface of the earth is (here R is the radius of the earth)
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$(\frac {n}{n+1}) mgR$
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$(\frac {n}{n-1}) mgR$
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nmgR
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$\frac {mgR}{n}$
Explanation
PE at height h (relative to infinity) minus PE at the surface, using g = GM/R²: ΔPE = GMm[1/R − 1/(R+h)] = GMm·h / [R(R+h)] = mgR·h/(R+h) (substituting GM = gR²) With h = nR: ΔPE = mgR(nR)/(R+nR) = mgR·n/(n+1) = [n/(n+1)]mgR.
Q.12
Two planets of radii $R_1$ and $R_2$ are made from the same material . The ratio of the accelerations due to gravity $g_1 /g_2$ at the surfaces of the planets is
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$\frac {R_1}{R_2}$
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$\frac {R_2}{R_1}$
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$(\frac {R_1}{R_2})^2$
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$(\frac {R_2}{R_1})^2$
Explanation
For planets of the same material (same density ρ), mass M = ρ×(4/3)πR³, so g = GM/R² = G×(4/3)πρR — directly proportional to R. So g₁/g₂ = R₁/R₂.
Q.13
Assertion: Total energy is conserved moving a satellite to higher orbit. Reason: Sum of change in PE and KE is same in magnitude and opposite in nature. Choose the correct one
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Both assertion and reason are true and reason is the correct explanation of the assertion
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Both assertion and reason are true but reason is not correct explanation of the assertion
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Assertion is true, but reason is false.
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Both assertion and reason are false.
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Reason is true but assertion is false
Explanation
The Reason's claim that the changes in PE and KE are equal in MAGNITUDE is false: for a circular orbit, KE = GMm/(2r) and PE = −GMm/r, so |ΔPE| actually works out to be exactly TWICE |ΔKE| (a consequence of the virial theorem for gravitational orbits), not equal. The Assertion (energy is conserved overall) is considered true in the sense that the total mechanical energy change of the satellite when raised to a higher orbit is properly accounted for by the external work done by the propulsion system — the general conservation-of-energy principle isn't violated, even though the satellite's own orbital energy does increase during the manoeuvre.
Q.14
What would be the acceleration due to gravity at another planet, whose mass and radius are twice that of the earth?
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g/4
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g/2
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g
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g/3
Explanation
g = GM/R². With mass 2M and radius 2R: g' = G(2M)/(2R)² = G(2M)/(4R²) = (1/2)(GM/R²) = g/2.
Q.15
The radii of circular orbits of two satellites A and B of the earth, are 4R and R, respectively. If the speed of satellite A is 3V, then the speed of satellite B will be
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3V/4
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6V
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12V
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3V/2
Explanation
Orbital speed v = √(GM/r) ∝ 1/√r. So v_A/v_B = √(R_B/R_A) = √(R/4R) = 1/2. With v_A = 3V: 3V/v_B = 1/2 → v_B = 6V.
Q.16
If we move from equator to pole, the value of acceleration due to gravity
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first increases then decreases
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remains same
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decreases
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increases
Explanation
The Earth is slightly oblate (flattened at the poles), so the poles are a bit closer to Earth's centre than the equator is — and the equator also experiences a small outward centrifugal effect from Earth's rotation that the poles don't. Both effects make g larger at the poles than at the equator, so g increases as you move from equator to pole.
Q.17
For a satellite moving in an orbit around the earth, the ratio of potential energy to kinetic energy is
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1/2
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2
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$\sqrt 2$
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$1/\sqrt 2$
Explanation
For a circular satellite orbit, KE = GMm/(2r) and |PE| = GMm/r. The ratio |PE|/KE = [GMm/r] / [GMm/(2r)] = 2.
Q.18
An artificial satellite moving in a circular orbit around the earth has a total (kinetic + potential) Energy $E_0$. Its potential energy is
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$E_0$
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$2E_0$
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$-E_0$
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$1.5E_0$
Explanation
For a circular orbit, the standard energy relations are KE = −E and PE = 2E (where E is the total orbital energy). So with total energy E₀, the potential energy is PE = 2E₀.
Q.19
The distance of a geostationary satellite from the centre of earth (radius R = 6400 km) is nearest to
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18R
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7R
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10R
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4R
Explanation
A geostationary orbit has a radius of about 42,000 km from Earth's centre. With Earth's radius R = 6400 km, that's about 42000/6400 ≈ 6.6R — closest to the option 7R.
Q.20
Assertion: The earth without its atmosphere would be inhospitably cold. Reason: All heat would escape in the absence of atmosphere. Choose the correct one
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Both assertion and reason are true and reason is the correct explanation of the assertion.
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Both assertion and reason are true but reason is not correct explanation of the assertion
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Assertion is true, but reason is false.
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Both assertion and reason are false
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Reason is true but assertion is false.
Explanation
Earth's atmosphere acts like an insulating blanket, trapping outgoing heat (the greenhouse effect) and keeping the surface much warmer than it would be if that heat simply radiated away unimpeded into space. Without an atmosphere, this trapped heat would escape freely, leaving Earth's surface far colder — the Reason directly explains the Assertion.
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