Download Uniform Circular Motion NOTES

Uniform Circular Motion
• "Uniform circular motion" means that a
body is changing directions at a constant
rate (that is, at a constant speed). It is not
speeding up or slowing down.
•Question for discussion #1: Is an
object experiencing uniform
circular motion accelerating?
Why or why not?
Uniform Circular Motion
Acceleration
•Recall that an object is accelerating, it is
either speeding up, slowing down, or
changing direction. So an object moving in
a circle with a constant speed is undergoing
an acceleration.
•Question for discussion #2: What
causes an object to accelerate,
according to Newton’s First and
Second Laws?
According to Newton’s First and
Second Laws, accelerations are
caused by unbalanced forces.
Question for discussion #3: What type of force
causes objects to move in a circle?
According to Newton’s First and
Second Laws, accelerations are
caused by unbalanced forces.
Question for discussion #3: What type of force
causes objects to move in a circle?
Answer:
Centripetal Forces!
ce in the same direction as the motion causes the object to speed up. A force
ctly opposite the direction of motion makes the object slow down. A force
pendicular to the direction of motion causes the object to change its path
m a line to a circle, without changing speed.
Centripetal Force
•centripetal means
ntripetal force is always directed toward the
ter of “center-seeking”
the circle in which an object moves.
agine tying a ball to the end of a string and
rling itdefined:
in a circle over
yourforce
head. The
string
any
that
rts the centripetal force on the ball to move it in
causes
object
to your
ircle. The
directionan
of the
pull is toward
d at the
center ofathe
circle. Notice
that the
follow
circular
path
ection of the centripetal force changes as the
ect moves around you.
If the ball
is on your
centripetal
forces,
ht, you pull to the
left
and
vice
versa.
therefore, can be any
ntripetal forces change direction so they remain
of
the
forces
we
have
nted toward the center of the circle.
•
•
so far discussed!
(Gravity, tension,
friction, etc.)
UNIT
What is the relationship bet ween
the centripetal force and the
object’s velocity?
centripetal force if its action causes
, a car can move in a circle because
e lack of friction on an icy road is
! Describe the relationship
between gravitational force,
mass, and distance
! Relate centripetal force to orbital
motion
Force depends on direction
erate by changing its speed or by
ection of the force (Figure 6.15). A
the force
(and
auses theWhen
object to speed
up. A force
akes thethus
object acceleration)
slow down. A force is
causes the object to change its path
peed. in the same direction
•
ward theas the velocity, the
moves.object is speeding up
ring and
he string
move it in
ard yourWhen the force (and thus acceleration) is
that the
s as thein the opposite direction as the velocity,
on yourthe object is slowing down
e versa.
•
a car can move in a circle because
lack of friction on an icy road is
between gravitational force,
mass, and distance
! Relate centripetal force to orbital
motion
Force depends on direction
ate by changing its speed or by
ction of the force (Figure 6.15). A
uses the object to speed up. A force
kes the object slow down. A force
auses the object to change its path
ed.
•
ard the
moves.
ng and
e string
ove it in
rd your
hat the
as the
on your
versa.
When the force
(and thus
acceleration) is
perpendicular to
the velocity, the
object is moving
in a circle
Question for Discussion:
What would happen if the
centripetal force was removed?
If the ball is
released at this
point, towards
which point will
the ball travel?
Why?
If you remove the force, the object will
move off in a straight line path, with a
constant speed, tangent to the circle
from the point of release. Recall Newton’s first law!
Anatomy of a Circle...MEMORIZE!
Velocity is TANGENT to the
circle. Force and Acceleration
point towards the center
(centripetal)!