## Universal law of gravity,quotes about life love and hate,nano write a book in a month - Try Out

Author: admin, 19.02.2014. Category: The Power Of Thinking

Gravity is a non-contact force (a force that can be exerted on a body without touching it), one of four fundamental non-contact forces we know of. The latter two are active only at distances as small as those present between protons and neutrons in the nuclei of atoms. Isaac Newton and others determined, mostly from astronomical data — observations of the motions of planets in the sky — that the gravitational attraction is a property of mass, that it is proportional to the product of the two masses involved, and that it is inversely proportional to the square of the distance between their centers of mass.
The graph on the right shows how the force of gravity (Fg) varies as one of the masses is increased from zero and the other is held constant. We generally think of gravity in terms of one variable mass and one fixed mass, like a planet. The universal law of gravitation is called an inverse-square law because the force is inversely proportional to the square of the distance between two masses.
The important thing about this feature of gravity is that if we double the distance between objects, the force of gravity is reduced by a factor of four (22), not two. Orbiting is a perfect balance between inertia, the tendency of a body to move in a straight line (not a curve) until acted upon by a force, and the attractive force of gravity. As the Moon orbits Earth, it has inertia, which always moves it in a direction tangential to the orbital path (nearly a circle).
Only a centripetal (center-seeking) force, like gravity, is required to keep bodies in orbit around one another. Here's another way to think about it: Imagine you've got quite an arm (QUITE an arm), and can throw a baseball very fast. Look at these two scenarios (left) First, you throw the ball at a velocity that produces a forward distance in a given time (let's say a second) that does not keep up with the downward distance caused by the pull of gravity. Now imagine that you throw the ball with sufficient speed that the curvature of Earth gives it enough extra height in any given period of time that the amount of distance it falls due to gravity is just enough to keep it a fixed distance away from the ground. That's really quite a speed, and it partly explains why it's so difficult to get objects to orbit Earth.

A 3 Kg newborn baby at the surface of Earth is gravitationally attracted to Earth with a force of about 30N.
Calculate the weight, in Newtons and in pounds, of the Mars curiosity rover, which has a mass of 899 Kg, on both Earth and Mars. How far apart (in meters) must two 1000 Kg spherical masses be in order to exert a 0.01 N force on each other? We can use the universal law of gravitation to find the acceleration of gravity near the surface of Earth (below). This is a good derivation to practice your skills with scientific notation and cancelling units. Notice that 9.8 mA·s-2 is the acceleration of gravity near the surface of Earth, where r = the radius of Earth. If we bring a negative and a positive charge together, the electrostatic force is attractive (brings them together). You can think of such constants as fixed numbers that are there for us to get the units correct. The force of gravity is greater on a more massive person than a less massive person, therefore the more massive person weighs more — weight, unlike mass, is a measure of force. The graph shows that when r, the distance between masses, is small, the gravitational force is high, but as r is increased, the force drops non-linearly. This idea underscores the notion that for a long time observers were stuck on the idea that there must be some force pushing in the direction of the motion. But for every bit of tangential motion, there is some inward motion that keeps the path bent exactly to the orbital path. How fast would you need to throw it so that as it travels, the bending away of the spherical Earth below it is just balanced by the downward distance it is pulled by gravity — it orbits just above the surface?
The forward inertia of the ball keeps it moving forward and gravity bends that path into a curve (an ellipse, actually).

Generally when we fire off a satellite, the rocket that carries it accelerates straight upward until it clears most of the friction-producing atmosphere, then turns over to accelerate to a tangential velocity that is fast enough to achieve a stable orbit.
Remember that ever body in the universe exerts a mass-proportional amount of gravity on every other body.
The location of the center of mass of the Earth-Moon system (the point where the two, if joined by a stick, would balance) is somewhere inside of Earth because Earth has about 6 time the mass of the moon. The dashed circle stays where it was at the beginning to help you see the circular motion of the larger planet. If we travel a substantial distance from the surface of Earth (it has to be big because r is so large), we would expect the acceleration of gravity to be smaller.
That makes sense, of course: If there's a baby carriage moving down the street, we pretty much expect the force to be applied from behind, not from the side. Thus while Earth exerts a force on the Moon that keeps it in orbit, the Moon also exerts a force on Earth.
Think of a seesaw: Where does the light person need to be in order to balance the weight of a heavy person?
There is no such repulsive component to the gravitational force; you never see someone walking down the street suddenly be ejected from the planet by gravity. All text and images on this website not specifically attributed to another source were created by me and I reserve all rights as to their use.

## Comments to «Universal law of gravity»

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