Transcript Uniform Circular Motion

Uniform Circular
Motion
What is uniform
circular motion?
 Movement of an object at constant speed
around a circle with a fixed radius
 Can the velocity be accelerated even though
it has constant speed?
 Yes, because the velocity may change due
to direction. If direction changes and
velocity changes then an object can
accelerate.
New terms for UCM
Term
Symbol Units
Example
Radius
r
m
3m
Centripetal
acceleration
Tangential
speed
Period
ac
m/s2
vT
m/s
2.5 m/s2 toward
the center
3.6 m/s
T
s
4.7 s
Centripetal
force
Fc
N
1.2 N toward the
center
Describing Circular Motion
 A lower case r represents the position of a
vector (the radius of the circle)
 The direction of the vector can change but
not its length (length is proportional to
magnitude, which is speed)
 The acceleration of an object in uniform
circular motion is always toward the center
of the circle, called centripetal acceleration
Circular Motion Equations
 Centripetal acceleration (ac)- acceleration of an
object in uniform circular motion.
• ac = vT2/r
 Tangential speed (vT)- speed at which an object
travels in a circular path.
• vT = 2πr/T
• an object will travel the distance of the circumference of the
circle, which is represented by C = 2πr
• Time required for one complete revolution around a circle is
called a period
– Symbol is T
– Units are seconds
What about net force?
 The force that causes centripetal acceleration is
called centripetal force
 For an object in UCM, what direction is the net
force?
 The same direction as the acceleration – toward
the center
 Fc = mac
 If you stop the acceleration, what direction will
the object move?
 The movement of the object is in the direction of
the velocity or tangent to the circle.