For an explanation, see the main splats page
SPLATS about force in physics
The principles of force in physics
- The four known and recognized forces of nature are the electromagnetic force, the gravitational force, the strong nuclear force and the weak nuclear force.
- The gravitational force exerted on a standard mass by an object depends on its mass, and on the square of the distance between their two centres of mass.
- The force of gravity obeys the inverse square law, and gravitational forces may be calculated using Newton's law of gravitation which is based on this.
- In 1674 Robert Hooke attempted to explain planetary motion as a balance of centrifugal force and gravitational attraction, but this failed to stand up.
- In 1665 Isaac Newton deduced the inverse-square gravitational force law from the 'falling' of the moon, rather than the apple of all the mythological accounts.
- In 1680 Isaac Newton demonstrated that the operation of the inverse square law on gravity leads directly to the formation of elliptical orbits in space.
- Gravitation is one of the four forces of nature. Although it may seem strong to us as we experience the force, it is a weak force which acts everywhere.
- In 1798 Henry Cavendish measured the gravitational constant with John Michell's torsion balance and from that, was able to determine the mass of the Earth.
- Based on the value of G and the known size of the Earth, Cavendish was able to estimate the density of the Earth at 5.48, close to the current value of 5.52.
- In 1749, Pierre Bouguer attempted to estimate the value of G, the Universal Gravitational Constant, using a mountain as an attracting mass, but it was too weak.
- The centrifugal force is a fictitious force, but there really is a force called the centripetal force. Either can be used in explanations and calculations.
- Under extreme conditions, the operations of gravity may lead to the formation of a black hole, a concentration of mass so great that even light cannot escape.
- Parabolic flight may be used to simulate 'weightlessness' near the Earth's surface, for short periods of time as an aircraft slows, turns over and falls freely.
- A centrifuge may be used to simulate high gravitational forces, relying on the accelerational forces used to keep rotating material moving in a circle.
- The understanding of the pendulum depends on understanding the forces involved, in particular, the restoring forces that operate in all forms of the pendulum.
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