Download Circular Motion and Torque

Circular Motion and Torque
Uniform Circular Motion
• Motion in a perfect circle (so the radius is
always the same) at a constant speed.
Frequency and Period
Period (T) – The time it takes for one revolution (one full
circle)
Frequency (f) – The number of revolutions per second,
this is measured in Hertz (Hz)
𝟏
T=
𝐟
𝟏
f=
𝐓
Tangential Velocity
• The speed and direction an object is moving in a
circle is called Tangential Velocity
This is because the direction is always
tangent to the circle
You can tell this by swinging
an object in a circle and then
letting go.
Tangential Velocity
Fire Spinners
in Thailand
Tangential Velocity
You can also feel this when you take a steep
turn in a car!
Vt
Vt
Tangential Velocity
vt =
2πr
T
vt = tangential velocity (m/s)
r = radius of circle (m)
T = Period (s)
f = frequency (Hz)
Centripetal Acceleration
Is an object moving in a perfect circle at a constant
speed accelerating?
Yes!! Remember that velocity involves speed AND
direction.
The direction is constantly changing so the object is
accelerating.
This is called Centripetal Acceleration
Centripetal Acceleration
Centripetal Acceleration - the acceleration of
something moving in a circle
Centripetal acceleration is ALWAYS INWARD
ac
ac
ac
ac
Centripetal Acceleration
ac=
2
v
r
ac= centripetal acceleration (m/s2)
v = tangential velocity (m/s)
r = radius of circle (m)
Centripetal vs. Centrifugal
• Centripetal means towards
the center
“Center-seeking”
• Centrifugal means away
from the center
“Center-fleeing”
Centripetal Force
Centripetal Force – The net force required to keep an
object moving in a circular path.
This could be a…
Frictional force
Tension force
Gravitational force
Centripetal Force
Centripetal Force is always acting towards the
center of the circle.
Fc
Fc
Fc
Fc
Centripetal Force
Fc = mac
Fc = Centripetal Force (N)
m = mass (kg)
ac = Centripetal Acceleration (m/s2)
Torque
Torque - a twisting forces that causes rotation
Objects rotate around the Axis of Rotation
(basically the center point)
Axis of
rotation
Torque
τ=Fr
τ = Torque (Nm)
F = Linear Force (N)
r = Radius (m)
Torque
The radius is how far from
the axis of rotation you
apply your force.
The further away you are,
the more torque you are
able to apply.
τ = Fr
As r increase, τ increases
Torque Examples
Have you ever tried
to open a door by
pushing/pulling near
the hinges?
Which wrench is
easier to use?
Torque Wrench