BBC - GCSE Bitesize: Mass and force
Newton's law of universal gravitation states that every particle attracts every other particle in the where F is the gravitational force acting between two objects, m1 and m2 are the masses of the objects, r is the distance . Newton's role in relation to the inverse square law was not as it has sometimes been represented. The weight of an object is the force on it due to gravity. There is a relationship between weight, mass and acceleration of free-fall (weight = mass × acceleration . Mass is a measure of how much matter an object contains, while weight is a measure of the force of gravity on the object. An object has the.
Observe how the force of gravity is directly proportional to the product of the two masses and inversely proportional to the square of the distance of separation.
Another means of representing the proportionalities is to express the relationships in the form of an equation using a constant of proportionality. This equation is shown below. The constant of proportionality G in the above equation is known as the universal gravitation constant. The precise value of G was determined experimentally by Henry Cavendish in the century after Newton's death. This experiment will be discussed later in Lesson 3. Using Newton's Gravitation Equation to Solve Problems Knowing the value of G allows us to calculate the force of gravitational attraction between any two objects of known mass and known separation distance.
As a first example, consider the following problem. The solution of the problem involves substituting known values of G 6. The solution is as follows: This would place the student a distance of 6.
Two general conceptual comments can be made about the results of the two sample calculations above. First, observe that the force of gravity acting upon the student a. This illustrates the inverse relationship between separation distance and the force of gravity or in this case, the weight of the student.Gravity, Force, and Work (clip)
The student weighs less at the higher altitude. However, a mere change of 40 feet further from the center of the Earth is virtually negligible. Apples fall to Earth because of gravity. Planets are drawn to the sun because of gravity.
- Newton's Law of Universal Gravitation
- Forces of Attraction
- Types of Forces
Newton's Law of Universal Gravitation The essential feature of Newton's Law of Universal Gravitation is that the force of gravity between two objects is inversely proportional to the square of the distance between them. Such a connection is known as an "inverse square" relationship. Newton derived this relationship from Kepler's assertion that the planets follow elliptical orbits.
Newton's law of universal gravitation - Wikipedia
To understand this, consider the light radiating from the surface of the sun. The light has some intensity at the surface of the sun. As the light travels away from the sun, its intensity diminishes. The intensity of the light at any distance away from the sun equals the strength of the source divided by the surface area of a sphere surrounding the sun at that radius.
Mass and force
As the distance away from the sun r doubles, the area of the sphere surrounding the sun quadruples. Thus, the intensity of the sun's light depends inversely on the square of the distance away from the sun. Newton envisioned the gravitational force as radiating equally in all directions from a central body, just as sunlight in the previous example.
Newton recognized that his gravitational model must take the form of an inverse square relationship. Such a model predicts that the orbits of objects around a central body will be conic sectionsand years of astronomical observations have borne this out. You exert a gravitational force on the people around you, but that force isn't very strong, since people aren't very massive. When you look at really large masses, like the Earth and Moon, the gravitational pull becomes very impressive.
The gravitational force between the Earth and the molecules of gas in the atmosphere is strong enough to hold the atmosphere close to our surface. Smaller planets, that have less mass, may not be able to hold an atmosphere. Planetary Gravity Obviously, gravity is very important on Earth. The Sun's gravitational pull keeps our planet orbiting the Sun.
Newton's law of universal gravitation
The Moon's gravity pulls on the Earth and makes the tides rise and fall every day. As the Moon passes over the ocean, there is a swell in the sea level. As the Earth rotates, the Moon passes over new parts of the Earth, causing the swell to move also.
The tides are independent of the phase of the moon. The moon has the same amount of pull whether there is a full or new moon. It would still be in the same basic place.
We have to bring up an important idea now.