Not just a crappy movie with Ice Cube httpwwwimpawardscom2004posterstorquejpg What Torque is Torque is a force that produces a rotation Think about using a wrench to turn a bolt Torque depends on TWO THINGS ID: 511408
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Slide1
Torque
Not just a crappy movie with Ice Cube
http://www.impawards.com/2004/posters/torque.jpgSlide2
What Torque is
Torque is a force that produces a rotationThink about using a wrench to turn a boltTorque depends on TWO THINGS:
How much force you applyHow far away from the center of rotation you apply it
http://upload.wikimedia.org/wikipedia/commons/2/21/Torque.JPG
If F
A
and F
B
are equal, which
will produce a greater torque
in this example?Slide3
Torque
The distance from the center of rotation to the location the force is applied is called the LEVER ARM.In general, we care about the part of the force that is applied
PERPENDICULAR to the lever arm
F
1
F
2
F
3
Let’s say that the lever arm rotates
around a pivot point to the left. If
all three forces are the same
magnitude, which one produces the
greatest torque?
Pivot
Lever armSlide4
Torque: strange units
Torque is kind of like force, ‘cept different.Force is a part of torque, but it also depends on that lever arm.
So torque is equal to force X length of the lever armForce is in Newtons
, Length is in meters
So torque is given in Newton-Meters (or in foot-pounds if you are in the English system).Slide5
Perpendicular Force
It’s just like when we were talking about vectorsA force at an angle will have a component that is perpendicular to the lever arm.What components of the forces below are perpendicular to the lever arms?Slide6
Torque brainstorm
Give some examples of torque that you use on a daily basisSlide7
Balanced Torques
Torques are forces (basically) and they can be in equilibrium with one another.Example: kids on a teeter-totter (or seesaw or whatever the youth of today call these devices).
Weight provides force, seesaw is lever armLet’s say you and a friend are on either end of a seesaw. If you weigh the same amount, then how far should each of you sit from the pivot?
Now assume the unlikely scenario that the two of you are different weights. Where should you sit?Slide8
Torque example: IGNORE CRAZY UNITS
http://microship.com/resources/resourcepix/cgdb-1.jpgSlide9
Rotational Inertia – Yes, it’s what you think
Remember inertia? Yeah, that was awesome.Inertia was the tendency of an object in motion to stay in motion.Likewise, rotational inertia is the tendency of an object that is rotating to keep rotating.
Just like it takes a force to change the linear state of motion, it takes a torque to change the rotational state of motion.Slide10
A subtle but important difference
For linear motion, inertia depends on massBut rotational inertia depends not only on mass, but also on its DISTRIBUTION
.The closer in the mass is to the center of rotation…
The less rotational inertia
The easier it is to get rotating
The easier it is to stop rotating once it starts
The farther the mass is from the center of rotation…
The greater rotational inertiaThe harder it is to get rotating
The harder it is to stop rotating once it startsSlide11
Examples and Demonstrations
“Choking up” on a baseball batShort Pendulum Vs. Long PendulumAnimals (including you) runningWeights on a bar
Flipping pencil between fingersRolling hoops and disks
Gymnastics and other spinning peopleSlide12
Angular Momentum
Rotational inertia of an object X how fast it’s rotatingAngular momentum can be conservedIf you change the rotational inertia, the rotational speed will also change to compensate
ExamplesGuy in chair with weights
Flywheels
Gymnasts