Physics 105, Fall Term, 2009
1) A force applied at a
distance from a pivot point creates a torque and causes rotational motion.
2) Torque is NOT a force.
3) Only the perpendicular force applied to
the 'lever arm' has an influence on torque.
What are the units of torque? (2 of the choices are correct, select all that
Newtons * meters
One of the above choices is correct, but confusing. Which is it and why is it
Joules is technically correct, but can be really confusing. This is because torque is not energy, even though they have are made up of the same units.
What units should you use for torque?
To see the affects of torque, go to:
http://phet.colorado.edu/sims/rotation/torque_en.jnlp and click on the
'Torque' tab at the top of the applet. The only graph you need to pay attention
to is the torque graph in the bottom right corner of the applet. You don't need
to put the bugs on the platform for this, but if you want to you can.
Type in a force value of 1 N and keep the radius at 4 mm and press 'Go'. Now
increase the force to 2 N. How does increasing the force affect the torque on
Torque stays the same
Now decrease the radius to 3 mm. How does decreasing the radius that the
force is applied at affect the
torque on the platform?
Now increase the force to 10,000 N and decrease the radius to 0 mm. What happens
when a large force is applied at the pivot point?
There is no rotation and no torque.
Which of the following increases for an object placed on the platform when
the platform is under a constant torque?
(Select all that apply)
Now go to:
The controls are very easy, just click anywhere within the applet box and it
will give you a force acting on the wrench. The farther you click from the
pointed end of the wrench the larger the force acting on it will be. The green
bar that shows up on the wrench shows the torque that is produced from the force
on the wrench. You can also click and drag to get a better idea of how changing
the angle affects the torque.
Click and drag the mouse in a circle (keep the distance from the pointed end up
the wrench the same). At what angle from the lever arm, the wrench in this case,
will the torque be the greatest?
The comments entered in these last two boxes go into a big anonymous data file that I will use to guide the lectures of the day. That means two things:
1) If you have a specific question or concern and would like an individual
answer you will need to come by the office or send an email.
2) If you really want to get an anonymous comment to me before the lecture, it
must be submitted before 11am that day.
Was there anything that you didn't understand in the reading assignment?
What was confusing to you?