Physics 2210 Fall 2012 Da\ id Ailion

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1 Physics 2210 Fall 2012 Da\ id Ailion j0qt\ Name: Vnid: ~ Exam IY F Discussion TA: -----~ Place a circle or box around each answer. SpecifY units for each answer. Report all numbers to two significant figures. Circle all that apply! A. [5 pts.] Which ofthe following statements are true for a soccer ball of mass m that is kicked with initial speed Vo at an angle (9 = 30 ) with respect to the horizontal on a calm, windless day in which air resistance can be neglected. (a) I (f) The range depends on the mass m ofthe ball. The range can be increased by using a lighter ball. The range maybe increased by kicking at a steeper angle (larger 9). The range may be decreased by kicking at a steeper angle (larger 9). The range would be greater if the same ball was kicked at the same angle on the moon. All ofthe above are correct. B. [5 pts.] The coefficient of static friction for the tires ofa race car is and the coefficient of kinetic friction is The car is on a level circular track of 50.0 m radius on Planet A where g =2.45 rnjs 2 If the car travels without slipping at the same maximum speed on the planet as on Earth, and ifthe coefficients offriction are the same on both planets, the radius ofthe track on Planet A must be how many times as large as the radius ofthe track on Earth? Circle the correct answer. (a) 0.25 (b) 0.50 (c) ~ 4.00 (e) None ofthe above. C. [5 pts.] Circle all that are (b) (c) ((d)) (e) The magnitude of the frictional force for kinetic friction is always given by Fk = IlkN. The magnitude ofthe frictional force for static friction is always given by F. = IlsN. The frictional force must be equal in magnitude to the applied force. The frictional force may be less than the applied force. The coefficient of kinetic friction Ilk is usually greater than 14, the coefficient ofstatic friction.

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3 Physics 221 () Fall 2012 David Ailion Name: tv A oj Vnid: ~ Discussion TA: 1 Exam 1 yp Report all numbers to two significant figures. Problem 1 - Continued D. [5 pts.} Three vectors A. B and C are shown in the drawing. If all three vector have the same length (2 m) and e=60 0 calculate the length ofthe resultant vector. ';01: -~ ~ V:;: 'ttg-tc Vx --:= 0 (<;!J111 rn:!f'';!f) Vj:::: (,6.ll~e t lei {Me - B tv 1= [Q]! A I ( tu>6oo -+ ars6oo- l ) D..-~ I! E. [5 pts.} Vector A = 4i -6]. vector B = J. and vector Cis unknown. However, the vector sum :5 =A+ B+ C=si + 4]. Calculate the angle that vector C makes with respect to the x-axis. <;0 I. D-:::,A+1S-fc,..) ~ ~ -.lo '-.. ~ "..J. ~ B ~ C D-A (5 i wf- q.j) - ( 4 ~ - 6J) -- (-1~ t 2 J) t~ t 8j

4 ~ " ~ I ~, Ph~ sics 2210 Fall 2012 Da\ ill Ailion Name: W,l \ Unid: Exam 1 Discussion TA: 2 Report all,umbers to two significant figures. [25 pts.} A soccer player kicks a ball horizontally off a 40.0 m high cliff into a pool of water. Ifthe player hears the sound ofthe splash 3.01 s later, what was the initial speed given to the ball? Assume the speed ofsound in air to be 343 mls. V., <-t}~ 'fj=-"lo! if 7OA( ts"'? b d t -;: ~.t r/- Vi:. - ds f ( C) -::"Yo -!-'\J 0-6 f- ~xt(, I(t) -::: V()i; p =~ot{: O-;:v~ 0J~ c,-: Vs (,-t~)~ fi;-;cv,ft)' V$ t 5 =-fil.. -t 0-:;:

5 Physics 2210 Fall 2012 Da\id Ailion J Name: -->d-,b~~----jr7~ral1-"'-1--t:_- Unid: Exam 1 3 Discussion TA: Report all numbers to two significant figures. M A light inextensible string connects two identical blocks, each of mass M as shown. The pulley and all surfaces are frictionless. (a) [5 pts.} Draw force (Le., free-body) diagrams for each mass. (b) [10 pts.} Calculate the tension T in the string in terms ofm, g, and 9. (c) [10 pts.} Now, assume that there is friction between the block on the plane and the surface of the plane, and the coefficients of kinetic and static friction, are respectively, J.lk and~. Calculate the tension T as the block slides down the plane in terms of these parameters and M, g, and 9. a) ft1& N T b) J) T+ "'JsiI({t) == t1! C{ d.)~tt-1f1j ;::. ~ )~A ~ ~T t-t11j5~e -vnj:=o mj LI-A1;"E1) d-.t=- T~ (I-~e) J1N N=~~e /' T I) ~4iA(j- t'4<.~~=~) ~.erjm J) -T;-vvt~ -=-rntt J,.T- tnjl/-~etfll<.~ej T ::: ~:1C,- /.).;;,; &+/1,<. ~e)

6 " ~.. Ph, sit's 221 {) Fall 2012 I).., ill \ilion Name: ".,..,. "JU",j\VJ ~{'i},d loy Unid: Exam 1 Discussion TA: 4 SHOW :lilt WORK!! Report all PBmben to two sipifleapt flipres. A person stands on a scale in an ascending elevator. The elevator starts from rest at the 4th floor with an acceleration that is constant until the elevator gets halfway to the 5 th floor. Between this point and the 5 th floor, the elevator slows down with a constant deceleration whose magnitude is the same as when it started. The distance between the two floors is 10m. Shortly after the elevator starts, the scale's reading is 560 N. Shortly before the elevator stops, the scale's reading is 380N.