Free Fall and Acceleration Due to Gravity Explained

The Problem Students Face

Have you ever stared at your physics textbook and wondered-“Why does every falling object have the same acceleration? Isn’t a heavy stone supposed to fall faster than a feather?” If yes, you’re not alone.

Many students struggle with the idea of free fall and acceleration due to gravity (g). The confusion usually comes from mixing everyday experiences with scientific principles. In daily life, we see leaves floating slowly, paper drifting in the air, or a cricket ball dropping quickly. This leads us to assume that heavier objects fall faster.

But in physics, especially when we talk about free fall, the situation is different. And misunderstanding this concept doesn’t just cause trouble in exams-it also affects your ability to understand more advanced topics like projectile motion, orbital mechanics, and satellite motion.

So, let’s clear the fog step by step in a way that you will never forget.

Why Misunderstanding Free Fall Causes Problems

Before we solve this puzzle, let’s think about what happens if you get it wrong.

In exams – You’ll often be asked to solve numerical problems involving free fall, velocity, and time. If you confuse “heavier objects fall faster” with reality, your calculations will be wrong.
In real-life physics – Free fall is the foundation for understanding why parachutes work, how satellites stay in orbit, or even how astronauts train in zero gravity. A small misunderstanding here can stop you from grasping these exciting applications.
In higher studies – Topics like Newton’s law of gravitation, projectile motion, and escape velocity are all connected to free fall. If your basics are shaky, the advanced concepts will feel impossible to crack.

So instead of memorizing formulas without understanding, let’s dive deep into what free fall really means, how gravity works, and why acceleration due to gravity is the same for all objects.

Step-by-Step Explanation

We’ll go step by step, starting with the basics, moving to real examples, and then working on practice problems.

1. What is Free Fall?

Definition: Free fall is the motion of an object when the only force acting on it is gravity.
That means no air resistance, no friction, no external push or pull—just gravity pulling it downwards.
Example: If you drop a stone in a vacuum chamber (no air), it will fall freely.

Non-example: A paper falling in the classroom is not in free fall because air resistance slows it down.

So, free fall is an idealized motion, but it helps us understand how gravity works.

2. What is Acceleration Due to Gravity (g)?

Whenever an object falls freely near the Earth’s surface, it accelerates towards the center of the Earth. This acceleration is called acceleration due to gravity, represented by g.
On Earth:

Average value of g = 9.8 meters per second squared (m/s²).

This means that every second, the object’s velocity increases by 9.8 m/s.

Example:

If you drop a ball, after 1 second it moves at about 9.8 m/s,
After 2 seconds, about 19.6 m/s,
After 3 seconds, about 29.4 m/s, and so on.
This constant acceleration is what makes free fall predictable.

3. Why Do All Objects Fall at the Same Rate?

This is where most students struggle. Let’s answer the famous question:
Does a heavy stone fall faster than a light feather?
In the presence of air, yes, the feather drifts slowly because of air resistance. But in a vacuum, where there’s no air, both fall together at the same rate.

Case Study: Galileo’s Experiment

In the 16th century, Galileo is said to have dropped two spheres of different masses from the Leaning Tower of Pisa.
Both hit the ground at the same time, proving that objects fall with the same acceleration regardless of mass.

Modern Confirmation: Apollo 15 ExperimentIn 1971, astronaut David Scott dropped a hammer and a feather on the Moon (where there’s no air). Both fell and hit the surface at the same time.

This experiment showed clearly that gravity acts equally on all masses.
So, mass does not matter. Gravity pulls everything with the same acceleration.

4. The Physics Behind g

Why is g equal to 9.8 m/s² on Earth?
Newton’s Law of Gravitation gives us the answer:
Force of gravity (F) = G × (M × m) / r²
Where:

G = gravitational constant = 6.67 × 10⁻¹¹ Nm²/kg²
M = mass of the Earth
m = mass of the object
r = radius of the Earth

But according to Newton’s second law, F = m × a.
So, equating the two:

m × a = G × (M × m) / r²

Cancel m from both sides:

a = G × M / r²

This acceleration (a) is what we call g.
Plugging in Earth’s values:

M = 5.97 × 10²⁴ kg
r = 6.37 × 10⁶ m
g ≈ 9.8 m/s²

That’s how the value is derived scientifically.

5. Motion Equations in Free Fall

When an object falls freely under gravity, we use the standard equations of motion with acceleration = g.

v = u + g t
s = u t + ½ g t²
v² = u² + 2 g s

Where:

u = initial velocity (0 if dropped)
v = final velocity
t = time
s = distance fallen

Example Problem:

A ball is dropped from rest from a height of 20 m. How long will it take to hit the ground?

Using: s = ½ g t²

20 = ½ × 9.8 × t²
20 = 4.9 t²
t² = 20 / 4.9 ≈ 4.08
t ≈ 2.02 s

So, the ball takes about 2 seconds to reach the ground.

6. Real-Life Applications of Free Fall

Now that we know the basics, let’s connect it with real-world situations:

Parachutes – Without air resistance, a parachutist would fall dangerously fast. Parachutes increase air resistance, reducing acceleration.
Bungee Jumping – Jumpers experience free fall until the rope stretches and applies an upward force.
Elevators – Safety brakes are designed so elevators don’t go into free fall in case of failure.
Sports – Cricket balls, basketballs, and long jumps all rely on understanding free fall and projectile motion.
Astronomy – Satellites are in continuous free fall around Earth, which is why they remain in orbit.

7. Common Misconceptions

Let’s clear a few doubts students usually have:

Heavier objects fall faster – False. They fall at the same rate if air resistance is absent.
g is exactly 9.8 everywhere – Not true. g varies slightly with altitude and latitude.

At poles: about 9.83 m/s²
At equator: about 9.78 m/s²

3 . Free fall means falling in vacuum only – Not exactly. Free fall means only gravity acts, so technically a satellite in orbit is also in free fall.

8. Practice Problems

Let’s test your understanding with a few interactive problems.

Problem 1

A stone is dropped from a cliff 45 m high. Find the time taken to reach the ground.

Solution:

s = ½ g t²
45 = ½ × 9.8 × t²
t² = 45 / 4.9 ≈ 9.18
t ≈ 3.03 s

Problem 2

An object is thrown downward with an initial velocity of 5 m/s. Find its velocity after 2 seconds.

Solution:

v = u + g t
v = 5 + 9.8 × 2
v = 24.6 m/s

Problem 3

A ball is thrown upward with velocity 20 m/s. How long before it comes back to the thrower’s hand?

Solution:

Time to rise = u / g = 20 / 9.8 ≈ 2.04 s
Total time = 2 × 2.04 ≈ 4.08 s

9. Fun Scenarios to Think About

If you drop your phone and a textbook together, which will hit the ground first? (In theory: both at the same time.)
Why do astronauts float in space even though gravity still acts on them? (Because they are in continuous free fall around Earth.)
If Earth’s radius doubled but mass stayed the same, what would happen to g? (It would reduce to one-fourth.)
These “what if” questions keep your mind active and help you apply concepts beyond the classroom.

The Takeaway

Let’s quickly revise what we learned:
Free fall means motion under the influence of gravity alone.
Acceleration due to gravity (g) is about 9.8 m/s² on Earth.
All objects fall at the same rate, regardless of mass, if air resistance is absent.
The equations of motion apply directly with acceleration replaced by g.
Real-life applications include parachutes, sports, space travel, and safety devices.

So, the next time you drop something, instead of panicking about your broken phone screen, ask yourself: “How fast was it moving when it hit the ground?”
That’s the fun of physics—you start seeing the world differently.

This guide gave you the problem (confusion about free fall), showed the consequences of misunderstanding, and provided a clear solution with explanations, examples, and practice.

Now you’re ready to solve any question on free fall and acceleration due to gravity with confidence.

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