Gravity, free fall and gravitational acceleration

Gravity is one of the most important forces in physics and everyday life. It is the force that pulls objects towards each other. Earth's gravity is what keeps us stationary on the planet. This concept involves many interesting aspects such as free fall and gravitational acceleration.

What is gravity?

Gravity is a force that attracts two bodies toward each other. Every object in the universe that has mass exerts a gravitational pull or force on every other mass. The size of the pull depends on the masses of the objects and the distance between them.

For example, the gravitational force of the Earth is much stronger than that of a small rock because the Earth has more mass. This natural force is represented by the symbol G. The gravitational force between two masses is described by the equation:

F = G * (m1 * m2) / r^2

Where:

• F is the force between the masses.
• G is the gravitational constant, which is approximately 6.674 × 10^-11 Nm²/kg².
• m1 and m2 are two masses.
• r is the distance between the centers of the two masses.

However, we don't often see small objects moving toward each other because the forces acting on them are very weak compared to the larger objects.

Visual example

Imagine two objects with different masses in space. Let's see how gravity works between them:

What is free fall?

Free fall is the motion of an object in which gravity is the only force acting upon it. In free fall, an object experiences constant acceleration. This condition can actually only occur in a vacuum, where there is no air resistance to slow down the falling object.

On Earth, air resistance affects freely falling objects, which means they do not fall at the same rate. However, if we neglect air resistance, all freely falling objects near the Earth's surface will accelerate downward at a speed of about 9.8 m/s². This is known as the acceleration due to gravity. This concept is represented by the symbol g.

Example of free fall

Suppose two objects, such as a feather and a hammer, are being dropped from the same height. Without air resistance, both the feather and the hammer would fall at the same rate.

Gravitational acceleration

Gravitational acceleration refers to the acceleration on an object due to the force of gravity. The gravitational pull of the Earth causes objects to fall toward the center of the Earth when you drop them. This means that as the object is falling, its speed is increasing by about 9.8 meters per second every second. Here's the formula for gravitational acceleration:

g = G * (M / r^2)

Where:

• g represents the acceleration due to gravity.
• G is the gravitational constant.
• M is the mass of the Earth (or of the body exerting the gravitational force)
• r is the radius from the center of mass to the object.

At the Earth's surface, the value of g is typically estimated as 9.8 m/s².

Effects of gravitational acceleration

Thanks to gravitational acceleration, everyday activities are possible. Let's consider some examples:

• When you throw a ball upwards, it is the gravitational acceleration that eventually stops its upward motion and brings it back to your hands.
• The Moon, which is closer to the Earth than the Sun, does not collide with the Earth because of the gravitational force and the tangential velocity of the Moon which produces an orbit.

Visualization of motion due to gravitational acceleration

Summary

In short, gravity is a fundamental force that governs the motion of objects both on Earth and in the universe. Free fall is the pure state of motion under the influence of gravity alone, showing how different objects behave when separated from other forces. Gravitational acceleration is the effect of gravity pulling objects toward a massive body, such as a planet, causing them to speed up as they fall. Understanding these concepts is essential to discovering the laws of physics that define our world.

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