Rotational Motion and the Law of Gravity Flashcards
Axis of rotation is the
center of the disk
Angular Displacement
The ____ is a unit of angular measure
➢ The ____ can be defined as the arc length s along a circle divided by the radius r
Radian
defined as the angle the object rotates through
during some time interval
Angular Displacement
This means that each part of the body is
fixed in position relative to all other parts of
the body
Rigid Body
ω, of a rotating rigid
object is the ratio of the angular displacement to
the time interval
Average Angular Speed
defined as
the limit of the average speed as the time interval
approaches zero
Instantaneous Angular Speed
➢ Speed will be ____ if θ is increasing
(counterclockwise)
➢ Speed will be ____ if θ is decreasing
(clockwise)
Positive
Negative
When the angular speed is ____, the
instantaneous angular speed is equal to the
average angular speed
constant
the change in its
angular speed Δω divided by Δt:
Average Angular Acceleration
the limit of the average acceleration
as the time interval approaches zero
Instantaneous Angular Acceleration
- An object traveling in a circle, even though it moves with a
constant speed, will have an acceleration - The ____ is due to the change in the direction
of the velocity
Centripetal Acceleration
Angular displacement,
velocity and acceleration are
all ____ quantities
Vector
o In a, the disk rotates counterclockwise, the direction of the angular velocity is out of the page
o In b, the disk rotates clockwise, the direction of
the angular velocity is into the page
Velocity Directions
➢ If the angular acceleration and
the angular velocity are in the
same direction, the angular speed will increase
with time
➢ If the angular acceleration and the angular
velocity are in opposite directions, the angular
speed will decrease with time
Acceleration Directions
states that the centripetal acceleration is accompanied by a force
Newton’s Second Law
➢ A puck of mass m is attached to a string
➢ Its weight is supported by a frictionless table
➢ The tension in the string causes the puck to
move in a circle
Centripetal Force Examples
The gravitational force exerted by a uniform
sphere on a particle outside the sphere is the
same as the force exerted if the entire mass of the
sphere was concentrated on its center
Gauss Law
