NEET (UG)

Practice Test 1 — Gravitation

12 questions • 18 minutes • auto-graded with full solutions

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Section A — MCQ (Single Correct)

Question 1

If the distance between two masses is halved, the gravitational force becomes:

Solution: $F \propto 1/r^2$; halving $r$ gives $4\times$.

Question 2

The acceleration due to gravity on a planet with $g = GM/R^2$ depends on:

Solution: $g$ depends only on the planet's mass and radius.

Question 3

Escape velocity from Earth's surface is:

Solution: $v_e = \sqrt{2gR}$.

Question 4

At a height equal to the Earth's radius, $g$ becomes:

Solution: $g_h = g R^2/(R+h)^2 = g/4$ at $h = R$.

Question 5

The orbital velocity of a satellite close to Earth's surface is about:

Solution: $v_o = \sqrt{gR} \approx 7.9\ \text{km/s}$.

Question 6

Weight of a body at the centre of the Earth is:

Solution: $g = 0$ at the centre, so weight $= 0$.

Question 7

For two planets, $T^2 \propto r^3$ is:

Solution: Law of periods = Kepler's third law.

Question 8

A satellite's total mechanical energy in orbit is:

Solution: $E = -GMm/2r$ for a circular orbit.

Section B — Assertion & Reason

Question 9

A: Escape velocity does not depend on the mass of the projected body.
R: In $v_e = \sqrt{2gR}$, the body's mass cancels out.

Solution: Mass cancels in the energy balance, so R explains A.

Question 10

A: A planet moves faster when it is nearer the Sun.
R: The angular momentum of the planet about the Sun is conserved.

Solution: Conservation of angular momentum (equal-area law) makes the planet speed up near the Sun — R explains A.

Question 11

A: The value of $g$ is exactly the same at the poles and at the equator.
R: The Earth's rotation and its equatorial bulge make $g$ vary with latitude.

Solution: $g$ is larger at the poles than the equator, so A is false; rotation and the bulge do make $g$ vary with latitude, so R is true.

Question 12

A: The total energy of a satellite in a bound orbit is negative.
R: A bound system needs extra energy supplied to reach infinity (zero energy).

Solution: Being bound (negative energy) means energy must be added to escape — R explains A.