The University of Colorado has graciously allowed us to use the following PhET simulation.
#Inverse square law gravity lab series#
Differences in gravitational forces from the moon acting on one side of the Earth, the center, and the other side of the Earth lead to tidal forces.Īt cosmological distances (much greater than the size of a galaxy) there is interesting current research on dark energy that shows that a previously unexpected repulsion happens with gravity at long distances, see here).įor more information on gravity please see here.īelow the PhET, there's a video from Scishow's series on fundamental forces, this one is on gravity. This means that if the distance is doubled the gravitational attraction is four times less. The gravitational force is an example of an inverse square law, meaning that the force drops with the square of the distance. The PhET simulation below shows how small gravitational forces are between human sized objects. Unless someone is taking very precise measurements in a lab (see for example Cavendish's famous experiment which determined the gravitational constant, G), the force of gravity must include only really big objects (like the sun, the moon or a planet) to be noticeable. Hydropower and tidal power are primary energy sources that take advantage of the gravitational force to generate useful work. When objects have the ability to fall, that's called gravitational potential energy. The force of gravity pulls us towards Earth, causing objects to fall. This force always attracts objects together, and although it is the weakest of the four fundamental forces, gravity has an infinite range. The gravitational force acts between all objects that have mass. r is the distance between the masses (in meters).m 1 and m 2 are the masses of the two objects (in kilograms).G is the gravitational constant and is 6.67 x 10 -11 N m 2/ kg 2.All masses attract other masses according to Newton's law of universal gravitation: The attractor position is modulated between a near and far position and the torque difference on the pendulum is recorded and analyzed for a possible inverse square law violation.The gravitational force (also referred to simply as gravity) is the force that pulls all the masses in the universe together. If the inverse square law holds, the gravitational field of the attractor is uniform and the torque on the pendulum is independent of the gap between pendulum and attractor.
The pendulum plate has an internal density asymmetry with a dense inlay on one half facing the attractor and another inlay on the other half on the side away from the attractor. The second experiment consists of a plate pendulum that is suspended parallel to a larger vertical plate attractor. The amplitude of the torque signal is analyzed as a function of the separation between the pendulum and the attractor. The torque on the pendulum disk varies as a function of the attractor angle with a 3 degree period. The attractor and the pendulum are disks with azimuthal sectors of alternating high and a low density.
The first experiment consists of a torsion pendulum that is suspended above a continuously rotating attractor. One experiment is designed to measure the distance dependent force between closely spaced masses, whereas the second experiment is a null experiment and is only sensitive to a deviation from the inverse square law of gravity.
I will present an overview of two experiments that are being conducted at the University of Washington to search for gravitational-strength deviations from the inverse square law for extra dimension length scales smaller than 50 micrometers. Such extra dimensions can be detected with inverse square law tests accessible to torsion balances. For sub-millimeter length scales there may be undiscovered, extra dimensions. Newton's inverse square force law of gravity follows directly from the fact that we live in a 3-dimensional world.
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