## Wednesday, February 24, 2010

### Period 2 Physics

Today, Wednesday, 2/24/10, you will be doing an online activity.

Multimedia Science School (in the Novell Screen)
Physics
Fields
Motion in a Circle
Lesson
Circular Motion

Go through the lesson doing all activities. Each GROUP must enter a summary of what you learned as a comment to this post. You may comment as "anonymous" but make sure the comment has all the names of the group members in it.

Solutions for the homework, problems 18-23, are below:

You can use "Ctrl and +" together to increase the size of the font and pictures on your screen.

If you are still having a hard time seeing the answers, you can go HERE and view or download them.

1. We learned that and object in a circle will always have a changeing velocity directed at a tangent to the circle.
The equation for centripetal acceleration is a=v^2/r, where v is the spped of the object and r is the radius of the circle.
The equation for the centripetal force is F=mv^2/r, where m is the mass of the object moving in a circle. The angle of a whole circle is 2pi radians. The period of rotation of an object moving in a circle is given by t=2pi/w. the centripetal acceleration can be written as a=rw^2. The centripetal force can be written as F=mrw^2. The angular velocity of an object moving in a circle is measured in radians per second and given the symbol w.

By Kevin E. Devissiere
Victoria Taiwo
Margarita Rodriguez

2. We found out that an object that moves in a circle has a changing velocity tangent to the circle and a changing centripetal acceleration towards the center of the circle. Objects moving in a circle at constant speeds have a uniform circular motion which has no tangential acceleration, a velocity which is constant and tangent to the circle, and centripetal acceleration changing direction directed towards the center of the circle. The formula for centripetal acceleration is a=v2/r and the equation for centripetal force is F=mv2/r.
The SI unit of an angle is called the radian. The radian is a unit of plane angle, equal to 180/π (or 360/(2π)) degrees, or about 57.2. The angle of a full circle is equal to 2π, by the same principle; a quarter of a circle is equal to π/2, and half a circle is π. The length of an arc in a circle is equal to r (angle), where the angle is in radians and r is the radius of the circle. As an object moves in a circular motion, its angular displacement can be described in radians i.e. half a circle is described as π and not 180 degrees. Centripetal acceleration is the rate of change of tangential velocity, the direction of the centripetal acceleration is always inwards along the radius vector of the circular motion. Centripetal acceleration is equal to r(w)to the second power. Within the circle, velocity can be measured as radians per second, just as they are used to measure displacement. Centripetal force can be written as mr(w)to the second power.
We learned that circular motion is able to be applied to all forms of objects known to man, the principles and equations can be used on all types or sizes of objects. In addition, centripetal forces can be in different types of forms, for example path of a roller coaster or the path of a race car track. The centripetal force must be provided by friction alone on a curve, and a increase in speed could lead to an unexpected skid if friction is insufficient can create something very unpleasant if there is no friction.

Boronny Touch