## Due 3:30 pm, Tuesday, October 20th

Physics 105, Fall Term, 2009

Did you complete the reading assignment?

Yes
No

## KEY CONCEPTS:

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 apply)

Newtons
Newtons * meters
Joules
Joules/meter

One of the above choices is correct, but confusing. Which is it and why is it confusing?

What units should you use for torque?

Newtons
Newtons * meters
Joules
Joules/meter

## Exercise 1

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 the platform?

Increases torque
Decreases torque
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?

Increases torque
Decreases torque
Torque stays the same

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?

Which of the following increases for an object placed on the platform when the platform is under a constant torque? (Select all that apply)

Linear velocity
Angular velocity
Centripetal acceleration
Angular acceleration
Centripetal force

Exercise 2

Now go to: http://www.usna.edu/MathDept/website/courses/calc_labs/wrench/TorqueWrench.html. 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?

30°
45°
60°
90°

FEEDBACK

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Was there anything that you didn't understand in the reading assignment?  What was confusing to you?