Review Problems for Final

These problems cover the whole range of things that you might see on the final. Each is a bit harder than the questions on the final will be, partly because they don't lead you through the steps involved in the problem - they expect you to think out the strategy for yourself. You can pick out and try the ones you think you might have trouble with.

The dog is trying to keep himself from moving. The person is pulling on his leash, with a force of 150 N at an angle of 30° from horizontal. What is the minimum coefficient of friction that will make this possible?
(Hint: be careful that all the forces balance. You can check your work by adding up all the component forms of the forces once you think you have them all)

Right now, I am at (10, -30), moving to the right at 10 m/s. Five seconds from now, I want to be at (10, 20). What should my acceleration vector be?
(Hint: just figure out what you know and start solving for other variables like in any motion problem)

A particular office building tends to sway back and forth, ten times per minute. The amount of sway is modest, but the engineers are concerned that it might make the building vulnerable to earthquakes, even very small ones. Why?




An earthquake wave travels quite fast, about 4000 m/s. How long would the earthquake wave need to be to be a danger to this building?


In the circuit shown above, use Thevenin equivalents to find the total resistance felt by the battery, and use that to find the current out of the battery. Then, determine the amount of current going through each other branch.

I rub a balloon against my hair, and hold it close to a large metal plate. I notice that a neutral foil ball hung near the far side of the plate (A) is being attracted to it. Explain why.




If I hold that same foil ball close to the side of the plate (B), will it be attracted, repelled, or unaffected?




If I touch the ball to the plate, it jumps away. What is the charge of the ball now? What about the plate?