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Physics 15] Roster No.:. SOLKUTIO NS Due: Friday, April 20, 2007 . Score: Fart A* 2 - poseible Take-Home Midterm Exam #3, Part A Total: SO pe. pombe NO exam time limit. Calculator required. All books and notes are allowed, and you may obtain help from others. Complete all of Part A AND Part B. For multiple-choice questions, circle the letter of the one best answer (unless more than one answer is asked for). For fill-in-the-blank and multiple-choice questions, you do NOT need to show your work. Show your work on all free-response questions, Be sure to use proper units and significant figures in your final answers. Ignore friction and air resistance in all problems, unless told otherwise. Physical constants: \t’s an open-book lest, so you can look them up in your textbook! Useful conversions: It’s an open-book test, so you can fock them up in your textbook! L. (4 pts.) Convert the following quantities into the given units. Fill in the blanks. (You do NOT need to show your work.) Use scientific notation where appropriate (very large or very small values), and express all fina! values to THREE significant figures. 4 los \ flmw) 2 age mW (5 «0 pad) iN ASS ww. LOC AID koh (+00 1% pe) Ca ey Lag. (aeons (2022 lo a. 9,85 x 107 MW = b. 3.00 x 10° unv/ns = c. $2,500 tpm = 0.20% ku rpm” =rev/min) = lot * ot be “Na, Boo tee. ev . ( ise) = 20g EY = 20¢ Ug fens om d. 19,300 kg/m? = 1%, 3 a tte mgm? (this is the density of gold) ‘ 1O-te, OS ke = 0,2 Nia,2008 (PELL ( at 19.3 May 2. A 430-g soccer ball flying directly to the left at speed v, strikes the head of a soccer player. The entire impact iasts 15 ms. Afterward, the ball rebounds directly to the right at the same speed v,. Express al] answers in MKS units: a. (2 pts.) If ¥,=21 m/s, what is the total impulse that the ball receives during the impact? ig 42 or N ad 3 b. (2 pts.) What is the average force that the ball exerts on the player’s head during part (a)? LZ¥*1O°N ee [200 N ¢. (2 pts.) The player’s head has a mass of 4.8 kg. The player wilt experience a concussion (brain injury) if his head undergoes an average acceleration greater than 75 gees. (1 gee = 9.80 m/s”. Ignore the head’s attachment to the rest of the player's body; just consider the head alone.) Assuming thai an impact always lasts 15 ms regardless of the value of v,, what is the minimum ball speed ¥, that will cause a concussion? 6 2 “/g (Fortunately, speeds this large are nor normally attained by soccer balls during play.) (a) Choose +irdweetion te the regbety Vea mit ~ Mb » Vibe fn “UY. Sapie BE MET mg oe) = me (oxy - Cog) > Apem AY, = (ome Uyy(a(2i"4) = 16.06 9% - (> By? ae \ By Newle’s 3% Law, Fy ow bead = Fay ou ball, and Tmpulte received by head bt 16 Same for tot head and ball, ave. fone acting oy ead wap of Wad = bp of ball. 
