The geometric model of gravity conceives the Earth as a collection of onion-skin layers, each with a uniform density and this is almost the case. Each individual sheet, because of its uniform density, has its center of mass corresponding to that of the Earth.
Nonetheless, if the layer has a small patch of higher density material, the center of the mass is shifted towards the patch, decreasing r, and thereby increasing g. Distance from Earth's Center m. Value of g. Earth's surface. As can be seen from both the equation and table above, the value of g varies inversely with the distance from the center of the earth.
In fact, the variation in g with distance follows an inverse square law, where g is inversely proportional to the distance from the center of the earth. Now observe that the mass of the object - m - is present on both sides of the equal sign.
Thus, m can be canceled from the equation. This leaves us with an equation for the acceleration of gravity. The above equation demonstrates that the acceleration of gravity is dependent upon the mass of the earth approx. If the value 6. And of course, the value of g will change as an object is moved further from Earth's center. For instance, if an object were moved to a location that is two earth-radii from the center of the earth - that is, two times 6.
As shown below, at twice the distance from the center of the earth, the value of g becomes 2. The table below shows the value of g at various locations from Earth's center. Distance from Earth's center m. As is evident from both the equation and the table above, the value of g varies inversely with the distance from the center of the earth.
In fact, the variation in g with distance follows an inverse square law where g is inversely proportional to the distance from earth's center. That's why you will see us emphasize that the outside of a helmet should be round and smooth to skid well on pavement. Without a helmet, hitting your head can transmit a thousand or more g's to your brain in about two thousandths of a second as you come to a violent, very sudden stop on the hard, completely unyielding pavement.
With a helmet between you and the pavement your stop is stretched out for about seven or eight thousandths of a second by the crushing of the helmet foam. That little bit of delay and stretching out of the energy pulse can make the difference between life and death or brain injury. Helmets do not "absorb" energy. Nothing does. The law of energy conservation says that a helmet can transform energy to work or to another form of energy, but can't absorb it.
That's why we refer to helmets as "managing" impact energy rather than absorbing it. Along with the stretching out of the impact, a helmet does change a small amount of the energy of a blow to heat as the molecules of foam move in the crushing of the foam.
To test that out for yourself, take a piece of picnic cooler foam on a hard surface and hit it with a hammer. The dent the hammer makes will be warm to the touch. And crushing foam is certainly work. Jul 16, Mar 31, Recommended for you. First observation of an inhomogeneous electron charge distribution on an atom 22 hours ago. Nuclear radiation used to transmit digital data wirelessly Nov 10, Load comments Let us know if there is a problem with our content. Your message to the editors.
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