PHY221 Ch3: Rel. Motion and Circular Motion

1. Relative Motion2. Accelerated frames and inertial frames3. Circular motion

PHY221 Ch3: Rel. Motion and Circular Motion1.

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Relative Motion: The relationship between expressed in reference frame F and in F’

OO’

x

x’

y’y

Example: swimming in a river:

r’r

P at t P at t+dt Relation between OP and OP’:

Relation between r and r’:

V river/groundV swimmer/river

PHY221 Ch3: Rel. Motion and Circular Motion1.

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Accelerating Frames have effects you can feel

Inertial frames are non-accelerating frames

Example of car accelerated w/ respect to Earth:

PHY221 Ch3: Rel. Motion and Circular Motion1.

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Uniform Circular Motion with v=cst at Radius=r

Centripetal acceleration in terms of v and r , or w and r :

Kinematics: relationship r, v and w:

Velocity vector Changes and acceleration from :

Components of :

PHY221 Ch3: Rel. Motion and Circular Motion1.

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Questions: What is the acceleration that the girl must generate on the rock for it to land at distance d from her feet (R is the length of string, and h the height of twirling plane above ground)

Rock twirl in hor. Plane above head. Which way when string is cut?

Ch 3: Assignments

Ch 3: Assignments