Introduction to Gravity
In physics, gravity is the universal force of attraction that operates between all matter. Gravitation was discovered by Newton in the year 1665, when he saw an apple falling down the tree. It is by far the weakest known force in nature and so has no bearing on the intrinsic characteristics of common matter. On the other hand, it influences the trajectories of bodies in the solar system and elsewhere in the universe, as well as the architecture and evolution of stars, galaxies, and the entire cosmos, due to its extended reach and ubiquitous activity. Each body on earth has a weight, or downward force of gravity, proportional to their mass, which is exerted by the mass of the earth.
What is Gravity ?
Gravity is the force that pulls items toward the centre of a planet or other entity. All of the planets are kept in orbit around the sun by gravity. Gravity exists in everything that has mass. Gravity is stronger for heavier objects. Gravity weakens with distance as well. As a result, the stronger the gravitational force of two things, the closer they are to each other. The gravity of the earth is caused by all of its mass. Its whole mass exerts a cumulative gravitational force on the entire mass of your body. That is what gives you heft. And if you were on a planet with a lower mass than earth, you would weigh less. The value of gravity on the surface of earth is 9.8 m/s2.
What Causes Gravity ?
In his theory of relativity, Sir Albert Einstein postulated that gravity is more than a force. According to him gravity is a curvature in the space-time continuum. Because the rubber sheet is distorted by the large ball's weight, this description is commonly seen as a heavy ball lying on a rubber sheet, with smaller balls sinking in towards the heavier object. Although the curvature of space-time cannot be observed directly in reality, it may be seen in the movements of things. Because the space it is travelling through is bent toward that object, every object under the influence of another celestial body's gravity is influenced.
What is Gravitational Force ?
Newton's law of gravity is used to describe gravitational force. It states that everyone in the universe attracts every other body with a force proportional to the product of their masses and inversely proportional to their distance. Gravitational pull is all around us. Consider two point mass bodies C and D of masses m1 and m2. Let r be the distance between their centres and F be the gravitational force of attraction between them and mathematically it is given as,
F=G m1m2/r2
Here G is the universal gravitational constant.
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Gravitational Force Examples in Our Daily Lives
There are various types of daily life examples which are based on gravitational force and help us in building the gravity concepts. Some daily life examples are,
The Objects' Stability: The objects on the earth's surface do not levitate or float in the air. This is due to the gravitational pull that exists between the items and the earth. Unless disrupted by an external force, the cup on the table does not float in the air and remains in the same spot. Gravity is also in charge of holding other items in place.
Formation of Tides: Tides are the periodic rise and fall of water in seas over a short period of time. These huge waves in the waters are created by the gravitational attraction of the moon and sun on the water present in the oceans. The oceans would be calmer in the absence of gravitational attraction because the magnitude of the tides would be reduced to one-third of their previous height.
Falling of Feather: A feather is an extremely light body that floats in the air. This light feather, on the other hand, gradually falls to the earth. The gravitational pull is exclusively responsible for this. A similar effect may be observed with any other light body, such as a piece of paper.
Walking: Walking is one of the most prevalent physical behaviours observed in practically every living terrestrial species. We do not float or perform levitation when walking since our feet are in close contact with the earth. Gravity, the ultimate phenomena, assists us in walking.
Application of Gravitational Force
The various applications of gravitational force are as follows,
This is used to compute the gravitational attraction of the planets in the cosmos.
It is also used to calculate the trajectory and anticipate the motion of celestial bodies.
It attracts all objects to the ground.
If there are no obstacles in the route, rocks and other things put on a slanting surface tend to roll down. The rolling of any physical body occurs as a result of gravitational force.
Drinks placed into a glass remain at the bottom and do not rise to the brim. This is made possible because of the application of gravitational force.
FAQs on Gravity on Earth
1. What is gravity on Earth?
Gravity on Earth is the fundamental force of attraction that the planet exerts on all objects, pulling them towards its centre. This force is a result of Earth's massive size and is what keeps everything, including the atmosphere and oceans, anchored to the surface. It causes an object in freefall to accelerate at approximately 9.8 m/s², a value known as the acceleration due to gravity (g).
2. What is the formula used to explain the force of gravity on Earth?
The force of gravity is explained by Newton's Law of Universal Gravitation. The formula is: F = G (m₁m₂ / r²), where:
- F is the gravitational force between the two objects.
- G is the universal gravitational constant.
- m₁ is the mass of the first object (e.g., the Earth).
- m₂ is the mass of the second object (e.g., a person).
- r is the distance between the centres of the two objects.
3. What are some real-world examples of gravity on Earth?
Gravity is constantly at work in our daily lives. Some key examples include:
- Objects Falling: An apple falling from a tree or a pen dropping from your hand are direct results of Earth's gravitational pull.
- Walking and Stability: Gravity keeps our feet firmly on the ground, allowing us to walk without floating away.
- Formation of Tides: The gravitational pull of the Moon and the Sun on Earth's oceans creates high and low tides.
- Planetary Orbits: Earth's gravity keeps the Moon in orbit around it, just as the Sun's gravity keeps Earth in orbit.
4. What is the difference between gravity and weight?
While related, gravity and weight are different concepts. Gravity is the fundamental force of attraction between two masses. Weight, on the other hand, is the measurement of the gravitational force acting on an object's mass (Weight = mass × g). An object's mass is constant everywhere, but its weight can change depending on the strength of the gravitational field. For example, you would weigh less on the Moon, even though your mass remains the same.
5. Is the acceleration due to gravity (g) the same everywhere on Earth?
No, the value of 'g' is not constant across the Earth's surface. The commonly used value of 9.8 m/s² is just an average. The actual value varies slightly due to two main factors:
- Earth's Shape: The Earth is not a perfect sphere; it's an oblate spheroid, slightly flattened at the poles and bulging at the equator. This means the poles are closer to the Earth's centre, resulting in a slightly stronger gravitational pull.
- Altitude: The force of gravity decreases as you move further away from the Earth's centre. Therefore, 'g' is slightly less at the top of a high mountain than it is at sea level.
6. Where is gravity the strongest and weakest on Earth?
Based on variations in Earth's shape and altitude, gravity is generally:
- Strongest at the poles, because they are closer to the planet's centre of mass.
- Weakest at the equator, because it is farther from the centre and also experiences a counteracting centrifugal force from the Earth's rotation. Gravity is also weaker at very high altitudes, such as on the summit of Mount Everest.
7. How does gravity on Earth compare to gravity on the Moon?
The Moon's gravity is significantly weaker than Earth's. It is approximately 1/6th the strength of Earth's gravity. This is because the Moon has a much smaller mass than the Earth. As a result, an object's weight on the Moon would be only one-sixth of its weight on Earth, which is why astronauts can jump much higher there.
8. What would happen if Earth's gravity suddenly stopped working?
If Earth's gravity were to suddenly disappear, the consequences would be catastrophic. Without the force holding everything down, the planet's angular momentum would cause anything not physically anchored to the bedrock to fly off into space. This includes people, buildings, vehicles, and all the water in the oceans. The atmosphere would also dissipate, and the Moon would no longer orbit the Earth, drifting away into space.
9. How far does Earth's gravitational influence actually extend?
Theoretically, the influence of Earth's gravity extends infinitely far into space. However, its strength decreases significantly with distance, following an inverse-square law. This means that while it never truly reaches zero, its effect becomes negligible compared to the gravitational pull of other, more massive or closer celestial bodies, like the Sun or Jupiter, at great distances.
10. What two factors primarily determine the strength of Earth's gravitational force?
The strength of the gravitational force between Earth and any other object is determined by two primary factors:
- Mass: The force is directly proportional to the product of the masses. The more massive the objects, the stronger the gravitational pull.
- Distance: The force is inversely proportional to the square of the distance between the objects' centres. The farther apart they are, the weaker the force becomes.
