Midterm Exam #2, Part A

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1 Physics 151 Mach 17, 2006 Midtem Exam #2, Pat A Roste No.: Scoe: Exam time limit: 50 minutes. You may use calculatos and both sides of ONE sheet of notes, handwitten only. Closed book; no collaboation. Fo multiple choice questions, cicle the one best answe o lette (unless moe than one answe is asked fo). Physical constants: g = 9.81 m/s 2 G = N m 2 /kg 2 Useful convesions: 1 y = s 1. (8 pts.) Convet the following quantities into the units specified. Fill in the blanks. (You do NOT need to show you wok.) Use scientific notation whee appopiate (vey lage o vey small values), and expess all final values to 3 significant figues. a Gy = s (see convesion facto above fo yeas [y] to seconds.) b Hz = THz c m 3 = cm 3 d g cm/s 2 = N 2. a. (2 pts.) A ca of mass m ounds a left-hand cicula tun with adius. If the oad is level (unbanked), and the ca poceeds aound the tun at constant linea speed v, what must be the minimum value of µ s fo the ca to stay on the oad and successfully execute the cuve? A. vg D. v g v 2 B. v 2 g E. g C. vg v 2 F. g 2 A B C b. (1 pt.) If the ca suddenly encountes an icy potion of the oad (at the moment shown hee) and µ s instantly becomes zeo, what will be the subsequent path of the ca? Cicle the ONE coect lette on the diagam at ight: ca: m D

2 3. A washing machine on spin cycle spins at appoximately 4.0 Hz when it gets up to full speed. a. (2 pts.) How much time is needed fo the machine to make one otation at this speed? A. 2.5 ms E. 85 ms B. 4.0 ms F s C. 25 ms G s D. 40. ms H s b. (3 pts.) If the washing machine s inteio is essentially a hollow cylinde of adius 0.25 m, what is the centipetal acceleation felt by the spinning clothes pessed against the inside edge? A times g E. 8.1 times g B times g F. 12 times g C. 2.6 times g G. 16 times g D. 5.1 times g H. 41 times g 4. (2 pts.) Which one of the following is TRUE? A. The gavitational foce of the Moon on the Eath is much smalle than that of the Eath on the Moon. B. The Moon is falling (acceleating) towad the Eath. C. The Moon s linea (tangential) speed constantly inceases ove time. D. If the mass of the Eath suddenly doubled, the Moon s obital speed would be unaffected. 5. (1 pt.) Keple s Second Law states that the imaginay line connecting the Sun and a planet sweeps out equal amounts of aea in equal intevals of time. As a esult, the linea speed of a planet in an elliptical obit A. must be constant at all points thoughout its obit. B. is slowest in the pat of its obit closest to the Sun, and fastest when fathest fom the Sun. C. is fastest in the pat of its obit closest to the Sun, and slowest when fathest fom the Sun. D. is fastest in the pats of its obit closest to and fathest fom the Sun, and slowest in between. 6. (2 pts.) A lase with a powe of 3.0 MW geneates a pulse of light fo 5.0 ms. What is the total enegy contained in the pulse? A J E. 600 J B. 1.7 J F. 1.7 kj C. 15 J G. 15 kj D. 85 J H. 85 kj 7. (1 pt.) An object slides down a stationay amp. The kinetic fiction foce on the object A. always points pependicula to the suface of contact B. always points opposite to the diection of the object s velocity C. has a magnitude that is popotional to the speed of the object D. has a magnitude that is popotional to the acceleation of the object

3 8. (8 pts.) Two identical masses m on Eath and Mas ae both dopped fom est, and both fall though identical heights h. (Ignoe ai esistance.) Suppose, fo simplicity, that g Mas = 1 3 g Eath exactly. a. The weight of the Eath mass is times the weight of the Mas mass. b. ΔU g fo the Eath mass is times ΔU g fo the Mas mass. c. ΔK fo the Eath mass is times ΔK fo the Mas mass. d. The final speed of the Eath mass is times the final speed of the Mas mass.

4 Physics 151 Mach 17, 2006 Midtem Exam #2, Pat B Roste No.: Scoe: Show you wok on fee-esponse questions. Be sue to use pope units and significant figues in you final answes. Physical constants: g = 9.81 m/s 2 G = N m 2 /kg 2 Useful convesions: 1 y = s Sun, Eath, & Moon data: masses adii obital distances obital peiods M Sun = kg R Sun = m M Eath = kg R Eath = m d Eath-Sun = m T Eath = 1.00 yea M Moon = kg R Moon = m d Eath-Moon = m T Moon = 27.3 days 1. a. (6 pts.) Geosynchonous satellites ae especially useful fo telecommunications, since they obit the Eath with a peiod of 1.00 day. (This makes them appea to hove above a single point on the Eath s equato in a stationay fashion, giving them thei name geosynchonous. ) Calculate the obital distance fom the cente of the Eath fo a geosynchonous satellite, assuming that its obit is pefectly cicula. Also, how many times R Eath (the adius of the Eath) is you answe? b. (4 pts.) The Intenational Space Station obits at a mean distance of only 1.06 R Eath fom the cente of the Eath fa close than a geosynchonous satellite. Assuming that both have pefectly cicula obits, which of the two obiting objects i. has the longe peiod? ii. has the faste linea speed? iii. has the geate centipetal acceleation? iv. feels the geate gavitational foce fom the Eath?

5 2. a. (5 pts.) Suppose that a 225-kg bobsled in last month s Winte Olympics stats a downhill un with an initial speed of 8.00 m/s. The sled descends a 45.0-mete-high hillside of vaying slope. Without fiction o ai esistance, calculate the bobsled s final speed at the bottom of the hill: b. (5 pts.) Now, suppose in eal life that fiction is pesent. The same bobsled stats with the same initial speed and descends the same hill as in pat (a), but its actual final speed at the bottom of the hill is only 24.0 m/s. How much enegy is dissipated by fiction duing descent? What pecentage of the bobsled s total initial enegy is this?

Chapter 5: Uniform Circular Motion

Chapter 5: Uniform Circular Motion Chapte 5: Unifom Cicula Motion Motion at constant speed in a cicle Centipetal acceleation Banked cuves Obital motion Weightlessness, atificial gavity Vetical cicula motion Centipetal Foce Acceleation towad