In Class 9 Physics (Gravitation), we study that the Earth attracts every object towards its center. But how exactly does an object behave when it falls? This is explained by the concept of Acceleration due to Gravity, denoted by the small letter 'g'.
Look closely at the formula $g = GM / R^2$. Notice that the mass of the falling object (small 'm') is not in the formula! This proves Galileo's famous theory: If there is no air resistance, an elephant and a feather dropped from the same height will hit the ground at the exact same time.
When an object is dropped from a height, it falls freely toward the Earth purely under the influence of Earth's gravitational pull. As it falls, its speed does not remain constant; it continuously speeds up (accelerates).
Definition: The uniform acceleration produced in a freely falling body due to the gravitational force of the Earth is called 'Acceleration due to Gravity'.
On the surface of the Earth, the average value of 'g' is 9.8 m/s². What does this actually mean? It means that if you drop a ball from a tall building, its downward speed will increase by 9.8 meters per second for every single second it spends in the air. (After 1 second, speed = 9.8 m/s. After 2 seconds, speed = 19.6 m/s, and so on).
According to Newton's Law of Universal Gravitation, the formula to calculate 'g' on any planet is: g = GM / R²
No. Because the Earth is not a perfect sphere (it is bulging at the equator and flat at the poles), the radius (R) changes. Therefore, **'g' is slightly higher at the Poles** and slightly lower at the Equator.
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