Download Circular Motion A rotation of an object about some axis, whether

Circular Motion
A rotation of an object about some axis, whether inside the object or outside the object leads to circular
motion. Just like in linear motion, an object at rest tends to stay at rest and an object in rotational
motion about an axis continues to be in that motion unless interfered with some external influence.
The property of an object to resist changes in rotational state of motion is called rotational inertia.
In linear motion the inertia is overcome by the application of Force. The rotational inertia is overcome
by the application of Torque.
When you use a wrench to tighten or loosen a bolt you use torque to create rotational motion
in the screw or lug nut. When you open a door, you apply a force at some distance from the axis of
rotation.
Torque = Lever arm ( distance) x Force
Any kind of force that causes an object to follow a circular path is called Centripetal
Force. Centripetal means towards the center. String tension force, Gravitational force or Electrical
force that is directed towards a fixed center is a Centripetal force. So any kind of force can become a
centripetal force if it directed towards the center.
Ex: When a can is whirled(turned) on the end of a string, we know that we must keep pulling at
the string to keep the can from falling down. The tension in the string transmits the centripetal force ,
pulling the can into a circular path.
Centripetal Force =
m = mass of the object; v = velocity of the object
r = radius of the circular path of object
Angular Velocity (ω ) is the rate of change of angular displacement (θ). It specifies the
angular speed of an object and the axis about which the object is rotating.
Angular acceleration is also called radial accelration. This acceleration is always directed
towards the center of the circular path. Objects moving in circular paths experience acceleration toward
the center even if they are going with constant velocity sice the direction is constantly changing.
Centripetal acceleration
v = velocity, r = radius of the circle
When objects are in circular motion, they experience an outward force. This outward force,
( directed away from center) is called Centrifugal force. The centrifugal force is caused by the inertia
of motion and is rather not a real force.
Planets tend to stay in the elliptical orbits because of the gravitational attraction between
their masses and the huge central object, the sun. It is not just planets that are attracted to Sun.
Everything that has mass attracts other things that have mass.
According to Newton, the force between any two bodies with mass m1 and m2 at a
distance of d from each other is directly proportional to the product of the masses and inversely
proportional to the square of the distance separating them.
G is called the universal gravitational constant. G = 6.67 x 10-11 N.m2/Kg2