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PHYSICS 111
Exam
November 29, 2007
Name: Signature:
Print your name and sign it legibly in the spaces provided above.
This exam consists of several questions, each consisting of possibly several parts of varying difficulty. If you cannot do one part, move on to the next part. Partial credit will be given throughout this exam. Show your line of reasoning; a final answer itself is not sufficient. To get ANY credit, you must show CLEARLY how you obtained your answers. If I cant read your work, or find your single answer, you wont get credit.
Please CIRCLE OR BOX YOUR ANSWERS, and always STATE THE UNITS if appropriate. If you need more space than what is provided, use the extra paper supplied by me.
If you are confused about a question, ASK for an explanation. Otherwise, I assume you understand EXACTLY what I was asking.
No exams will be accepted after 9:00 PM.
Some helpful constants you might need for this exam.
100 cm = 1 m 1000 g = 1 kg 1 day = 86, 400 s Iring = M R^2
I. Rolling hula hoop (12 points)
A hula hoop is rolling down Jefferson Ave. The intersection with the light at the top is approximately 30 m higher than the bottom of the hill. The hula hoop has a mass of 0. 65 kg and a radius of 0. 42 m. The hoop is given an initial speed of 1. 2 m/s at the top of the hill. What is the linear speed of the hula hoop at the bottom of the hill?
II. Swing (8 points)
At a nearby playground, you find a small child who is on the swings. You measure the period of the swing to be 1. 9 s. Treating the swing as a simple pendulum, how long is the swing?
IV. Pogo stick (12 points)
You have decided to take up a new sport, extreme pogo stick! You step horizontally from the top of a loading dock which is 3. 3 m above the ground on your pogo stick. The spring compresses 0. 25 m until you come to rest at the turnaround point which is 0. 10 m above the ground. The total mass of you and the pogo stick is 82 kg. What is the spring constant for the spring in the pogo stick?
V. Ranking (18 points)
Below are shown two disks with different radii as indicated in the figure. The two disks are rotating such that point A and B both have a constant tangential speed, vt = 6 m/s. Rank the following quantities for points A and B, circling your answer – no explanation is required, but any reasoning can be used to give partial credit.
30 cm
A
B
60 cm
(a) (6 points) angular velocity ω A = B A > B B > A not enough information
(b) (6 points) angular acceleration α A = B A > B B > A not enough information
(c) (6 points) centripetal acceleration ac A = B A > B B > A not enough information
