rotational motion and the law of gravity causes of circular motion
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Rotational Motion and Rotational Motion and the Law of Gravitythe Law of Gravity
Causes of Circular MotionCauses of Circular Motion
Force That Maintains Circular Force That Maintains Circular MotionMotion
Objects that travel in circular paths Objects that travel in circular paths have forces that maintain that have forces that maintain that circular motioncircular motion– Called Force that maintains circular Called Force that maintains circular
motion (Fmotion (Fcc))
– Measured in Newtons (N)Measured in Newtons (N)– Must be directed toward the center of Must be directed toward the center of
the circular paththe circular path
Force That Maintains Circular Force That Maintains Circular MotionMotion
Force that maintains circular motion Force that maintains circular motion = mass * centripetal acceleration= mass * centripetal acceleration– FFcc=ma=macc
Force that maintains circular motion Force that maintains circular motion = mass * (tangential speed)= mass * (tangential speed)22/radius/radius– FFcc=mv=mvtt
22/r/r Force that maintains circular motion Force that maintains circular motion
= mass * radius * (angular speed)= mass * radius * (angular speed)22
– FFcc=mr=mrωω22
Describing the Motion of a Rotating Describing the Motion of a Rotating SystemSystem
Inertia is often misinterpreted as a Inertia is often misinterpreted as a forceforce– Centrifugal forceCentrifugal force
Not a forceNot a force
In order to maintain circular motion, In order to maintain circular motion, the force that maintains circular the force that maintains circular motion must overcome inertiamotion must overcome inertia
Newton’s Law of Universal Newton’s Law of Universal GravitationGravitation
Gravitational force – the mutual force of Gravitational force – the mutual force of attraction between particles of matterattraction between particles of matter
Every pair of objects experience gravitational Every pair of objects experience gravitational attraction between themattraction between them
Most objects do not notice this attractionMost objects do not notice this attraction– Objects’ masses are too small and the distance between Objects’ masses are too small and the distance between
them is too largethem is too large– Gravity is only noticeable over short distances when one Gravity is only noticeable over short distances when one
object is very large (planet or moon-sized)object is very large (planet or moon-sized)– When both objects are very large, the gravity is When both objects are very large, the gravity is
noticeable at larger distances (sun and planets noticeable at larger distances (sun and planets gravitational attraction keeps the planets in orbit)gravitational attraction keeps the planets in orbit)
Newton’s Law of Universal Newton’s Law of Universal GravitationGravitation
Gravitational force = constant * Gravitational force = constant * (mass 1 * mass 2)/(distance between (mass 1 * mass 2)/(distance between center of masses)center of masses)22
FFgg=Gm=Gm11mm22/r/r22
G=6.673*10G=6.673*10-11-11 Nm Nm22/kg2/kg2 Gravitational force is concentrated at Gravitational force is concentrated at
the center of a spherical massthe center of a spherical mass