Fun with Gravity – Long Answer Questions (CBSE Class 10 Physics)

Medium Level (Application & Explanation)

Answer:

In free fall, an object moves under gravity alone. No other forces act, not even air resistance.
Newton’s Second Law says F = ma. In free fall, the only force is weight (F = mg).
So, ma = mg, which means the acceleration a = g (about 9.8 m/s²).
This shows all objects have the same acceleration in free fall, no matter the mass.
In a vacuum, this is exactly true. On Earth, air resistance can change motion.
Examples: A ball dropped from a height, or a ball thrown up and coming down are free fall (ignoring air).

Answer:

The acceleration due to gravity (g) is about 9.8 m/s² near Earth’s surface.
The weight of an object is the gravitational force on it: W = F = mg.
From this, g = F/m. We can find g if we know force (weight) and mass.
Example: If F = 19.6 N for a mass m = 2 kg, then g = 19.6/2 = 9.8 m/s².
The value of g is slightly different at different places on Earth.
It is less at the equator and more at the poles because of Earth’s shape and rotation.

Answer:

When thrown up, the object moves against gravity, so it slows down.
Its acceleration is always downward, equal to g (about 9.8 m/s²).
At the highest point, its velocity becomes zero for a moment, but acceleration is not zero.
As it falls back, it speeds up due to the same g downward.
If we ignore air resistance, the upward and downward motions are symmetric.
This whole motion is due to Earth’s gravitational pull acting continuously.

Answer:

Mass is the amount of matter. It is constant and does not change with place.
Weight (W = mg) is a force. It depends on g and can change with location.
Since g varies slightly on Earth, weight also varies slightly.
g is greater at the poles and less at the equator, so weight is more at poles.
So, the same gold has different weight at different places, but same mass.
This is why we measure goods by mass (kg), not by weight (N), for fairness.

Answer:

The sheet has a larger surface area and faces more air resistance.
Air resistance acts upward and opposes the motion of falling objects.
The crumpled ball has less area and faces less air resistance.
So, the crumpled ball falls faster and reaches the ground sooner.
In a vacuum (no air), both would fall together with the same g.
Thus, the difference is due to air resistance, not due to mass.

Answer:

In a vacuum, only gravity acts, so both have the same acceleration g.
So, they will hit the ground together, as mass does not affect g.
In air, both still have g downward, but air resistance now matters.
The lighter stone (often with more area per mass) is slowed more by air.
The heavier stone has less effect from air resistance and often falls faster.
Conclusion: Same time in vacuum; in air, shape and area change the fall.

Answer:

The force on her is weight, given by F = mg.
Newton’s law says F = ma. So, ma = mg, and a = g.
The mass cancels out, so acceleration in free fall is independent of mass.
Thus, Ria’s mass does not change her acceleration due to gravity.
What can change is air resistance, which can slow motion a bit.
In a vacuum, absolutely all objects fall with the same g.

Answer:

Weight is W = mg. Take g ≈ 9.8 m/s² near Earth’s surface.
So, mass m = W/g = 700/9.8 ≈ 71.4 kg. His mass stays the same everywhere.
At the equator, g is slightly less than at the poles.
Therefore, W = mg will be slightly less at the equator.
His mass (71.4 kg) does not change, but weight (in N) is a bit smaller.
This difference happens because of Earth’s shape and rotation.

Answer:

The Sun’s gravity pulls planets toward the Sun, and Earth’s gravity pulls the Moon toward Earth.
Planets and the Moon also have sideways motion due to their inertia.
Gravity provides a centripetal force, constantly changing direction of motion inward.
The objects keep missing the central body and thus circle around it.
Without gravity, they would move in a straight line and fly away.
With gravity, they keep curving and stay in stable orbits.

Answer:

In a vacuum, there is no air, so no air resistance acts.
The only force on both objects is gravity: F = mg.
From F = ma, we get a = g for both, regardless of mass.
So, both the feather and the hammer have the same acceleration.
They fall together and hit together when dropped from the same height.
On Earth with air, the feather faces large air resistance, so it falls slower.