Gravitation — NEET Physics MCQs with answers

Gravitation is a Class 11 Physics chapter in the NEET (UG) syllabus. NEET720 has 748 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.

Topics covered

Variation of g with altitude · Weight variation with position · Null point of a gravitational field · Variation of g with altitude and depth · Energy of a satellite · Variation of g due to rotation of the Earth · Binding energy · Effect of the Earth's rotation on g · Energy conservation in a gravitational field · Mass of the Earth · Work in changing orbits · Kepler's second law · Surface gravity and density · Near-surface orbital period · Universal law and variation of g · Gravitational field and potential · Field of a spherical shell · Escape and orbital speeds · Change in potential energy · Projectile in a gravitational field · Satellites and Kepler's laws · Energy of orbiting bodies · Gravity inside the Earth · Superposition of forces · Geostationary satellite · Geostationary orbit radius · Orbital motion · Angular momentum in orbit · Satellites and orbital mechanics · Potential of a spherical shell · Energy of an orbiting satellite · Kepler's laws and orbital mechanics · Gravity on other bodies · Weightlessness and apparent gravity · Weight at altitude · Escape speed and orbital speed · Escape velocity and density · Binary star system · Potential of a solid sphere · Satellite drag

8 free Gravitation practice questions with answers

Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.

1. Question 1 · medium · Satellites and Kepler's laws

   A remote-sensing satellite must photograph the entire surface of the Earth at high resolution over the course of many orbits. The most suitable orbit is:

   • A.a geostationary orbit
   • B.a low-altitude polar orbit
   • C.a low-altitude equatorial orbit
   • D.any orbit whose period is exactly 24 hours
   Show answer and explanation

   Answer: B. a low-altitude polar orbit

   A low polar orbit passes over the poles while the Earth rotates beneath it, so successive orbits sweep out adjacent north-south strips; low altitude gives high resolution. Together these let the satellite cover the whole globe.

   In a polar orbit the plane of the orbit contains the Earth's axis. As the satellite completes each roughly 100-minute revolution, the Earth turns about 25 degrees underneath it, so each pass photographs a fresh longitudinal strip; in about a day the whole surface is scanned. Low altitude (typically 500–900 km) is essential for high spatial resolution. A geostationary satellite (option A) has the complementary virtues — continuous view of one region, ideal for communication and weather monitoring of that region — but can neither see the poles nor resolve fine detail from 36,000 km. A low equatorial orbit (option C) never leaves the tropics.

   Common mistake: Defaulting to 'geostationary' for every satellite application

2. Question 2 · easy · Satellites and Kepler's laws

   A telecommunication company wants a satellite that always stays above the same point on the Earth's equator, so ground antennas never need to be re-aimed. The satellite must be placed in:

   • A.a low polar orbit, since polar orbits pass over every point on Earth
   • B.any circular orbit, as long as its altitude exceeds a few hundred kilometres
   • C.an orbit as close to the Earth's surface as possible, to minimise signal delay
   • D.a geostationary orbit, with period equal to the Earth's rotation period and orbit in the equatorial plane
   Show answer and explanation

   Answer: D. a geostationary orbit, with period equal to the Earth's rotation period and orbit in the equatorial plane

   To remain fixed relative to a ground point, the satellite's angular velocity must match the Earth's rotation, which requires a specific equatorial orbit — the geostationary orbit at about 36,000 km altitude with a 24-hour period.

   A satellite appears fixed in the sky only if it orbits in the equatorial plane with exactly the Earth's rotational period and in the same sense (west to east). This condition, via Kepler's third law, fixes a unique orbital radius (~42,000 km from Earth's centre). A polar orbit (option A) gives global coverage over time but is never fixed relative to one point. Any arbitrary circular orbit (option B) generally has a different period, so the satellite drifts relative to the ground. A very low orbit (option C) actually has a short period (~90 min), making the satellite race across the sky many times a day — exactly the opposite of what is needed for a fixed communication link.

   Common mistake: Believing any high-altitude or low-altitude orbit can keep a satellite fixed over a point

3. Question 3 · medium · Satellites and Kepler's laws

   An astronaut inside an orbiting space station experiences apparent weightlessness (floats freely). This happens because:

   • A.the Earth's gravity is zero at the station's altitude
   • B.the station is far enough from Earth to be outside the range of gravitational attraction
   • C.the station and astronaut are both in continuous free fall around the Earth, so there is no relative (normal) force between them
   • D.the centrifugal force exactly cancels gravity everywhere inside the station, making net force truly zero in an inertial frame
   Show answer and explanation

   Answer: C. the station and astronaut are both in continuous free fall around the Earth, so there is no relative (normal) force between them

   Both the station and the astronaut fall freely under gravity with the same acceleration, so the astronaut exerts no normal force on the station's floor — this is 'weightlessness', not the absence of gravity.

   Gravity is very much present at orbital altitude and is precisely what curves the station's path into a circle (or ellipse) around the Earth — without it the station would fly off in a straight line. Weightlessness arises because both the astronaut and the station accelerate towards the Earth at the same rate (gravitational acceleration depends only on position, not mass), so there is no relative acceleration between them, and hence no contact (normal) force is needed to keep the astronaut 'in place' relative to the station — exactly like the sensation in a free-falling lift. Option A and B incorrectly claim gravity is absent; option D invents a fictitious centrifugal force that only appears in a rotating (non-inertial) reference frame and should not be treated as literally cancelling gravity in the inertial description of orbital motion.

   Common mistake: Believing there is no gravity in orbit or in space near Earth

4. Question 4 · medium · Satellites and Kepler's laws

   According to Kepler's first law, a planet moves in an elliptical orbit with the Sun at one focus. This means:

   • A.the Sun is at the geometric centre of the ellipse
   • B.the planet's distance from the Sun varies continuously as it orbits, except in the special case of a circular orbit
   • C.the Sun's position shifts between the two foci during the year
   • D.there must be a second, invisible body located at the empty focus
   Show answer and explanation

   Answer: B. the planet's distance from the Sun varies continuously as it orbits, except in the special case of a circular orbit

   Because the Sun sits at one focus rather than at the ellipse's centre, the planet's distance from the Sun changes throughout the orbit, reaching a minimum at perihelion and a maximum at aphelion — except for a circular orbit, which is the special case of zero eccentricity.

   An ellipse has two foci; Kepler's first law places the Sun at one of them, not at the centre. A defining property of an ellipse is that the sum of distances from any point on it to the two foci is constant, but the distance to just one focus (the Sun) varies as the planet moves around — smallest at perihelion, largest at aphelion. Only when the eccentricity is zero does the ellipse degenerate into a circle, and both foci merge at the centre, giving a constant orbital distance. The empty focus in option D is a mathematical feature of the ellipse's geometry and does not require a physical object there.

   Common mistake: Treating the focus of an ellipse as if it were the centre

5. Question 5 · medium · Satellites and Kepler's laws

   A satellite is launched into an equatorial circular orbit with a period slightly less than the Earth's rotation period of 24 h. As seen by an observer on the ground, this satellite will appear to:

   • A.remain perfectly fixed in the sky, just like a true geostationary satellite
   • B.immediately fall out of orbit, since only exactly 24 h periods are physically allowed at that altitude
   • C.drift slowly westward relative to the ground, falling behind the Earth's rotation
   • D.drift slowly eastward relative to the ground, completing extra 'laps' relative to the Earth over time
   Show answer and explanation

   Answer: D. drift slowly eastward relative to the ground, completing extra 'laps' relative to the Earth over time

   A period slightly shorter than 24 h means the satellite completes each revolution a little faster than the Earth turns, so relative to the ground it slowly gains, drifting eastward and slowly changing its longitude over successive orbits.

   For the orbit to appear perfectly fixed, its period must equal the Earth's rotation period exactly (about 23 h 56 min, the sidereal day) and lie in the equatorial plane. If the period is even slightly shorter, the satellite finishes each orbit a bit before the Earth has completed one rotation, so its sub-point on the ground creeps eastward orbit after orbit — this small mismatch is exactly why real geostationary satellites need station-keeping thrusters to correct drift caused by orbital perturbations. A period longer than 24 h would instead cause a westward drift. The satellite remains safely in a valid circular orbit throughout (ruling out option B); it just does not stay above one fixed point.

   Common mistake: Assuming any near-24 h orbit stays effectively fixed over the ground

6. Question 6 · easy · Variation of g

   At a height h = R/200 above the Earth's surface (R = Earth's radius), the percentage decrease in the value of g compared to its surface value is approximately:

   • A.1%
   • B.0.5%
   • C.2%
   • D.0.25%
   Show answer and explanation

   Answer: A. 1%

   For h<<R, g_h ≈ g(1-2h/R), so % decrease = 2h/R×100 = 2(1/200)×100 = 1%.

   For small heights (h << R), g_h = g/(1+h/R)² ≈ g(1 - 2h/R). Percentage decrease = (2h/R)×100 = 2×(R/200)/R×100 = 2×(1/200)×100 = 1%.

   Common mistake: Omitting the factor of 2 that arises from the binomial approximation

7. Question 7 · medium · Time period of satellite

   A satellite revolves very close to the Earth's surface (radius R, surface gravity g). Its time period of revolution is given by:

   • A.2π√(R/g)
   • B.2π√(g/R)
   • C.2π√(R³/g)
   • D.(1/2π)√(R/g)
   Show answer and explanation

   Answer: A. 2π√(R/g)

   T=2π√(R³/GM); using GM=gR², T=2π√(R³/gR²)=2π√(R/g).

   For a circular orbit, T = 2π√(r³/GM). For a satellite orbiting just above the surface, r ≈ R. Using GM = gR², T = 2π√(R³/(gR²)) = 2π√(R/g).

   Common mistake: Forgetting to simplify R³/R² to R after substituting GM

8. Question 8 · medium · Gravitational field

   Two point masses, 4 kg and 9 kg, are placed 5 m apart. The gravitational field intensity is zero at a point on the line joining them, located at a distance from the 4 kg mass of:

   • A.2 m
   • B.2.5 m
   • C.3 m
   • D.1.5 m
   Show answer and explanation

   Answer: A. 2 m

   At the null point, x/(5-x) = √(4/9) = 2/3, giving x = 2 m.

   Let the null point be at distance x from the 4 kg mass. Field intensities balance: Gm₁/x² = Gm₂/(5-x)². So (x/(5-x))² = m₁/m₂ = 4/9, giving x/(5-x) = 2/3. Solving: 3x = 2(5-x) ⇒ 3x = 10-2x ⇒ 5x=10 ⇒ x=2 m.

   Common mistake: Assuming the neutral point lies exactly at the geometric midpoint regardless of mass values

Questions about Gravitation for NEET

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Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (748 active practice questions in this chapter today).