Acceleration due to Gravity — Definition

Definition

Imagine you drop a stone. It falls towards the Earth, right? This 'falling' isn't just happening randomly; it's because the Earth is pulling the stone towards its center with a force called gravity. As a result of this gravitational pull, the stone starts moving faster and faster as it falls.

This increase in speed, or more precisely, the rate at which its velocity changes, is what we call 'acceleration'. When this acceleration is caused *only* by the Earth's gravity, we call it 'acceleration due to gravity', and we represent it with the letter '$g$'.

Think of it this way: if you're standing on the Earth's surface, the Earth is constantly trying to pull you towards its center. If you were to jump, you'd immediately be pulled back down. The speed at which you accelerate downwards (ignoring air resistance) is $g$. On average, near the Earth's surface, this value is approximately $9.8,\text{m/s}^2$. This means that for every second an object falls, its downward speed increases by $9.8$ meters per second.

It's crucial to understand that $g$ is an acceleration, so its unit is meters per second squared ($ext{m/s}^2$). It's also a vector quantity, meaning it has both magnitude (how strong it is) and direction (always pointing towards the center of the Earth).

While we often use $9.8,\text{m/s}^2$ as a standard value, $g$ isn't truly constant. It changes slightly depending on where you are on Earth. For instance, it's slightly less at high altitudes (like on a mountain) because you're further from the Earth's center.

It's also slightly less at the equator compared to the poles due to the Earth's rotation and its slightly flattened shape. Understanding these variations is key to mastering this concept for NEET.