Unit 3: Circular Motion Summary
In Unit 3 we learned about Circular Motion, which is the study of objects rotating around an object in a circular partner, hence Circular Motion. This is seen with planets rotating around stars or objects rotating around planets. One important element that makes circular motion possible is an inward force; this is also called the centripetal force. A circular motion has two kinds. Uniform and non-uniform. In uniform motion, the object travels along at a constant speed. This does not take into account the object’s velocity, which is the change of speed or direction, because a rotating object is always changing its direction.
Terminology
Axis of rotation - the center around which an object rotates
Uniform circular motion - is motion in a circular path with constant speed
Centripetal acceleration - Centripetal acceleration points toward the center of the circular path of the train, but is felt by passengers as a force pushing them to the outer edge of the circular path
Centripetal force - Is a force acting toward the center of the circle causing the object to move in a circular path
Centrifugal force - is the reaction force exerted by the rope on the hand
Period - is the time required to complete one circle
Frequency - is the number of cycles per second
RPM - Rotations Per Minute. Similar to Frequency, but every 60 seconds.
Orbital period - is the time taken for a given object to make one complete orbit around another object
Orbital radius - is the distance between what an object is orbiting around and the object itself at any given poin
Satellite - an object that orbits planets, ie satellites orbiting earth.
Centripetal force
What is centripetal force?
Centripetal force is the force acting on an object that is moving in a circular path and is directed toward the center around which the object is moving. A few examples are record discs spinning in circles, a car taking turning in a circular path or tying an object to a string and spinning it in circles. For objects in uniform circular motion, the net force and acceleration is towards the center of the circle. Circular motion requires an inward or centripetal force, or else the object would just be going in one direction.
Centripetal force is the force acting on an object that is moving in a circular path and is directed toward the center around which the object is moving. A few examples are record discs spinning in circles, a car taking turning in a circular path or tying an object to a string and spinning it in circles. For objects in uniform circular motion, the net force and acceleration is towards the center of the circle. Circular motion requires an inward or centripetal force, or else the object would just be going in one direction.
Kepler's Laws
Kepler's First Law - All planets in the solar system have elliptical orbits, with the Sun at one focus.
Kepler's Second Law - A planet will not stay at a constant speed. A line drawn from the center of the sun to the center of the planet will sweep out equal areas
Kepler's Third Law - The ratio of a planet's orbital period squared to its orbital radius cubed is a constant. All planets orbiting the same focus (ie, sun) have the same constant
Satellite
A satellite is any object that is orbiting the earth or any massive body. Satellites can be categorized as natural satellites or man-made satellites. The moon, planets and comets are examples of natural satellites, these satellites orbit the earth are called natural satellites and are a launched from earth for purposes of communication. Centripetal force is provided by gravity. Were it not for this force, the satellite in motion would continue in motion at the same speed and in the same direction. In other words, it would go in one direction until a force acted on it making it move in another direction. Occasionally satellites will orbit in paths that can be described as ellipses.