NEET Physics: acceleration due to gravity and its variation with altitude and depth Practice Questions

Correct answer: D — mg

The gravitational force (F) exerted by the gravitational field (g) on a body of mass (m) is defined as F = mg.

Correct answer: B — the acceleration due to gravity changes.

Weight (W=mg) depends directly on the local acceleration due to gravity (g). If g changes (due to altitude or depth), the weight of the object will change, even if its mass (m) remains constant.

Correct answer: C — Decreases

The acceleration due to gravity decreases as the altitude increases because the gravitational force weakens with distance from the center of the Earth.

Correct answer: D — Because the force of gravity exerted by the celestial body is uniform and far away

In a vacuum far from any mass, the gravitational influence becomes negligible, and the concept of a uniform acceleration due to gravity is not applicable in this context, although the concept of gravitational field exists. For simple conceptual recall related to altitude variation, the concept breaks down far away. (Alternatively, if we consider 'no gravity' far away, the variation ceases.)

Correct answer: C — g' = g/4

The acceleration due to gravity varies inversely with the square of the distance from the center of the Earth (g ∝ 1/r²). If the altitude (distance r) is doubled, the new gravity will be 1/(2²) times the original gravity, which is 1/4 of the original.

Correct answer: A — 1/4

The acceleration due to gravity g is inversely proportional to the square of the distance (g ∝ 1/r²). If the distance r is doubled (2r), the new acceleration will be g' = g / (2)² = g/4. Thus, the change factor is 1/4.

Correct answer: B — 9.8 m/s²

The standard and commonly accepted value for the acceleration due to gravity (g) near the Earth's surface is approximately 9.8 m/s² (or 9.81 m/s² for more precision).

Correct answer: D — the oblateness of the Earth

The variation in g with altitude is primarily caused by the Earth's rotation and the resulting non-spherical shape (oblateness) of the Earth, which dictates the local gravitational pull.

Correct answer: D — It becomes one-fourth

The acceleration due to gravity (g) varies inversely with the square of the distance (r) from the center of the Earth. If distance is doubled (2r), g becomes g/(2²) = g/4.

Correct answer: A — g is inversely proportional to r

The acceleration due to gravity is inversely proportional to the square of the distance from the center of the mass (g ∝ 1/r²), which is a fundamental concept of gravitational field variation.

Correct answer: C — g decreases linearly with altitude.

As altitude increases, the distance from the center of the Earth increases, and the gravitational force decreases proportionally to the square of the distance (g ∝ 1/r²). Therefore, the acceleration due to gravity decreases as altitude increases.

Correct answer: A — Less than the acceleration due to gravity at the surface.

Inside a uniform fluid, the gravitational force is still acting, and the apparent acceleration due to gravity is reduced. The acceleration due to gravity inside a body is given by g = g₀ (1 - d/R), where d is the depth and R is the radius. Therefore, g inside the fluid is less than g at the surface.

Correct answer: B — At the center

The acceleration due to gravity is zero only at the geometric center of the Earth because the gravitational pull from all directions cancels out there.

Correct answer: B — It would be one-fourth

Acceleration due to gravity (g) depends on the mass and radius of the body. If we consider the Earth as a point mass, the gravitational field strength outside the mass is still governed by the inverse square law, meaning g decreases with distance. While the approximation is complex, the fundamental concept is that gravity decreases with distance from the source mass.

Correct answer: B — Weight is directly proportional to g

Weight (W) is defined as mass (m) times local gravitational field strength (g): W = mg. Therefore, weight is directly proportional to the local gravitational field strength.