# Warm-Up Exercise for lecture 9

## Due 8:00 am, Tues, Sep 29

Physics 105, Fall 2009

Enter your 3-digit class identification number:

Enter the last 4 digits of your BYU ID:

Did you complete the reading assignment? (Typically this means at least 20-30 minutes looking over the assigned sections of the book.)
☐ yes ☐ no

You compress a spring 10 cm from its equilibrium position. Then you compress it another 10 cm. In which step did you do more work?
☐ The first 10 cm
☐ The second 10 cm
☐ Both cases involve the same amount of work.

Switchbacks on mountain roads (consider only work done against gravity):
☐ increase the work needed to go up a mountain
☐ decrease the work needed to go up a mountain
☐ keep the work needed the same

Switchbacks on mountain roads (consider only work done against gravity):
☐ increase the power needed to go up a mountain
☐ decrease the power needed to go up a mountain
☐ keep the power the same

Ralph sees that his car's engine is rated at 100 hp. He thinks, "Cool, this means if I ever get in a tug of war with 90 horses, I will win!" Is he thinking about this correctly? What should you tell him?

The comments in the next next two boxes go into a big, mostly anonymous text file that I skim through before the morning lecture, using the comments to help me plan class discussion. ("Mostly anonymous", because I can track down who made what comment, but it takes some effort on my part to do so.) Therefore, if you really want to make sure I see your question/comment and answer it individually, you should send it to me via email and not through this form.

Which part of today's assignment was particularly hard or confusing? What would you like to spend extra time on in class?