## Friday, February 12, 2010

### Physics Period 1 - Friday Feb 12th

Today 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.

Below is the solution for problem 22 from the homework (thanks to Sherwin).

1. Sherwin Yu
Emmanuel Torres
Kevin Pham

Circles are very critical in physics for there are many different types of forces acting upon an object traveling in that circle. When an object is traveling in a circle the direction is constantly changing, therefore the velocity will always be changing. The speed is only constant whenever it has reached maximum speed. Centripetal force and acceleration are always directed towards the center of the circle. An object moving in a circle will always have a centripetal acceleration that is perpendicular to the velocity.

2. Alyssa Zargos, Alex Soares, Kevin Andrade.

Speed and velocity in a moving object going in a circle differs. The speed of an object moving in a circle only has magnitude, and no direction. Also velocity has direction and magnitude. During moving objects, the speed is constant when it has reached maximum speed, and it changes as it starts up and stops. Also the velocity is never constant because it is always slowing down and starting up. An object moving at a constant speed in a circle is said to have uniform circular motion. When circular motion is uniformed tangential acceleration is equal to zero. An object moving in a circle would always a changing velocity at a tangent to the circle. Also, there is a changing centripetal acceleration directed towards the centre of the circle and perpendicular to the velocity. The equation a = v2/r is to figure out centripetal acceleration, and to figure out centripetal force is F = mv2/r. The constants v = speed of the object, r = radius of the circle, and m = the mass of the object moving.

There are a few different ways to measure angles. The SI unit of the angle is called a radian. The radian is defined as the angle that starts at the center of the circle by an arc on the circumference that is equal in length to the radius of the circle. The angle of a whole circle is 2pi radians. The length of any arc is equaled to r-theta. Theta equals the angle in radians. The angular displacement of an object moving in a circle is measured in radians and given the symbol theta. The centripetal acceleration is known as a = rw, and the force is equaled as F = mrw2.

The principles and equations of circular motion can be applied to the motion of objects on all scales, including subatomic particles. The centripetal force can be provided by a variety of different forces and combinations of forces. The contribution of weight of an object to the centripetal force will vary.

3. Within this section of physics, we learn about circular motion and its effects on how everything moves around us. We learned that an object moving in a circle will always have a changing velocity directed at a tangent to the circle and along with this, we learned that a changing centripetal acceleration directed towards the center of the circle. Centripetal acceleration is the rate of change of tangential velocity. Now, an object moving in a circle at constant speed is said to have uniform circular motion. The rules for uniform circular motion there are that there are no tangential acceleration, there must be a velocity which is constant in magnitude, there must a changing direction and directed at a tangent to the circle, there must be a centripetal acceleration which is constant in magnitude, changing direction and directed to the center of the circle, and also a centripetal force which is constant in magnitude, changing direction and directed to the center of the circle.
The equation for centripetal acceleration is:
a = v2/r, where v is the speed of the object and r is the radius of the circle.
The equation for centripetal force is:
F = mv2/r, where m is the mass of the object moving in a circle.

bryan,hernan, Mohammed, Sindy.....We are not finished

4. Nefertiti Ferguson-Goforth; Marissa Martinez, Lizzette Martinez
You don’t need an arrow for speed because speed is a scalar quantity and only has magnitude, not direction.
You need an arrow for velocity because Velocity is a vector quantity and has direction and magnitude.
The speed of an engine is constant when the engine has reached it maximum speed. Velocity is never constant when the engine reaches it maximum speed.
The wheel only has tangential acceleration when the wheel is speeding up and slowing down.
The tangential acceleration and velocity are the same when an object, such as a Ferris wheel, speeds up but when the object slows down the tangential acceleration and the velocity are inverse.
Centripetal acceleration increases as the magnitude of velocity increases.
When an object reaches constant speed, its tangential acceleration is zero.
Formula: a = v2/r

5. Cynthia Garcia
Precious Humphrey
Elizabeth Trejo
Roneisha Handy
Selina Meach
Phyllisse Lewis

Objects in circular motion have changing velocities because they’re changing their directions of motion. Uniform circular motion is when an object moves in a circle at a constant speed. The equation for centripetal acceleration is velocity squared divided by the radius. The equation for centripetal force is mass times velocity squared divided by the radius. 2π radians are equal to the angle of a whole circle since 2π equals 360º. We use radians to measure the angular displacement of an object moving in a circle.

6. I learned that speed is a scalar quantity and only has magnitude and not direction, and that Velocity is a vector quantity and has both direction and magnitude. When the engine of the object has reached its maximun spped it had a constant speed and changes in velocity. When and object is moving in a cirlce, the magnitude of the centripetal acceleration relates to that magnitude and velocity because it increases as the velocity increases. The tangenial acceleration vector is 0 when the wheel moves at a constant speed. Speed is magnitude of velocity. a=v2/r is the relashionship b/w centripetal acceleration and speed. Centripetal force= Fmv2/r.
In centripetal force the weight and magnitdues are constant. The objects going in a vertical cirlce, the centripetal foce will vary.

-Naelia B.