Search results
Mar 4, 2015 · When being asked for the weight force, it is generally implicitly understood, it's the gravitational force of an object on the earth (or it will be specifically called out on what body and the acceleration due to gravity on that body, e.g. find the weight force of a person of 68 kg mass on the moon which has an acceleration due to gravity of $1.620 \dfrac {m}{s^2}$).
Oct 17, 2024 · Accessed 13 November 2024. Weight, gravitational force of attraction on an object, caused by the presence of a massive second object, such as the Earth or Moon. Weight is a consequence of the universal law of gravitation: any two objects, because of their masses, attract each other with a force that is directly proportional.
- The Editors of Encyclopaedia Britannica
- Overview
- Early concepts
gravity, in mechanics, the universal force of attraction acting between all matter. It is by far the weakest known force in nature and thus plays no role in determining the internal properties of everyday matter. On the other hand, through its long reach and universal action, it controls the trajectories of bodies in the solar system and elsewhere in the universe and the structures and evolution of stars, galaxies, and the whole cosmos. On Earth all bodies have a weight, or downward force of gravity, proportional to their mass, which Earth’s mass exerts on them. Gravity is measured by the acceleration that it gives to freely falling objects. At Earth’s surface the acceleration of gravity is about 9.8 metres (32 feet) per second per second. Thus, for every second an object is in free fall, its speed increases by about 9.8 metres per second. At the surface of the Moon the acceleration of a freely falling body is about 1.6 metres per second per second.
The works of Isaac Newton and Albert Einstein dominate the development of gravitational theory. Newton’s classical theory of gravitational force held sway from his Principia, published in 1687, until Einstein’s work in the early 20th century. Newton’s theory is sufficient even today for all but the most precise applications. Einstein’s theory of general relativity predicts only minute quantitative differences from the Newtonian theory except in a few special cases. The major significance of Einstein’s theory is its radical conceptual departure from classical theory and its implications for further growth in physical thought.
Newton argued that the movements of celestial bodies and the free fall of objects on Earth are determined by the same force. The classical Greek philosophers, on the other hand, did not consider the celestial bodies to be affected by gravity, because the bodies were observed to follow perpetually repeating nondescending trajectories in the sky. Thus, Aristotle considered that each heavenly body followed a particular “natural” motion, unaffected by external causes or agents. Aristotle also believed that massive earthly objects possess a natural tendency to move toward Earth’s centre. Those Aristotelian concepts prevailed for centuries along with two others: that a body moving at constant speed requires a continuous force acting on it and that force must be applied by contact rather than interaction at a distance. These ideas were generally held until the 16th and early 17th centuries, thereby impeding an understanding of the true principles of motion and precluding the development of ideas about universal gravitation. This impasse began to change with several scientific contributions to the problem of earthly and celestial motion, which in turn set the stage for Newton’s later gravitational theory.
Britannica Quiz
All About Astronomy
The 17th-century German astronomer Johannes Kepler accepted the argument of Nicolaus Copernicus (which goes back to Aristarchus of Samos) that the planets orbit the Sun, not Earth. Using the improved measurements of planetary movements made by the Danish astronomer Tycho Brahe during the 16th century, Kepler described the planetary orbits with simple geometric and arithmetic relations. Kepler’s three quantitative laws of planetary motion are:
1.The planets describe elliptic orbits, of which the Sun occupies one focus (a focus is one of two points inside an ellipse; any ray coming from one of them bounces off a side of the ellipse and goes through the other focus).
2.The line joining a planet to the Sun sweeps out equal areas in equal times.
The weight of an object mg is the gravitational force between it and Earth. Substituting mg for \ (F\) in Newton’s universal law of gravitation gives. \ [mg = G\dfrac {mM} {r^2}, \] where \ (m\) is the mass of the object, \ (M\) is the mass of Earth, and \ (r\) is the distance to the center of Earth (the distance between the centers of mass ...
The force acts towards the centre of the planet and is measured in newtons (N). of an object is the gravitational force between the object and the Earth. The weight of an object depends upon its ...
Weight is the force acting on an object due to gravity - it has the unit newtons (N) and acts towards the centre of a gravitational field. So weight is a gravitational force on an object that has ...
People also ask
Why is weight a gravitational force?
What is gravitational force in physics?
What is the difference between weight and force of gravity?
What is the force of gravity on an object?
How does gravity affect weight?
Why is gravity a force that attracts objects towards each other?
We will also occasionally speak of this force of gravity as the weight force. This is just equivalent terminology, two different names for the same thing. The weight force is often indicated by a . Again, it’s a vector, so again, it would be, the weight force would be the mass of the object times , where this is still the 9.8 newtons per ...
