2012 Sepember 25 Eam I Physics 105 Circle he leer of he single bes answer. Each uesion is worh 1 poin Physical Consans: Earh s free-fall acceleraion = g = 9.80 m/s 2 3. (Mark wo leers!) The below graph displays he elociy,, of an objec as a funcion of ime. Mark wih an X he labeled ime when he objec has achieed is maimum posiion. Circle he labeled ime when he paricle has he maimum acceleraion. (Noe: negaie numbers are smaller han any posiie number.) 1. The posiion,, of a cerain paricle is gien by he euaion: = acos(b 2 )+c 3 where is he ime. The dimensions (L = lengh, T = ime) of a, b and c are respeciely: (cm/s) 20 10 10 20 A B C D 1 2 3 4 5 6 Time (s) A. L, L/T 2, T 3 B. L/T 2, L/T 2, L/T 3 C. L, L T 2, T 3 D. L, 1/T 2, L/T 3 2. How many of he below numbers display eacly 3 significan digis? 30 4. Saring from res, a car acceleraes down a sraigh road. A shor ime laer he drier applies he brakes, and he car comes o a sop. Which of he below graphs of posiion s. ime bes displays his moion? 0.090 5.02 A B 70.0 0.00742 0.72 0.720 720 7210 0.63 10 4 39.1 10 14 A. fie B. si C D C. seen D. none of he aboe
5. A boy hrows a sone sraigh up. Which of he below graphs bes displays he elociy of he sone during is up-and-down fligh? A C 6. The below displays he ecors p and in arious orienaions. The ecors always hae he same lengh, only he orienaion is changing. Circle he case in which + p is he larges. A p B B D p 7. An ice dancer glides hrough a oally dark arena. A flashing srobe locaes her a successie seconds (shown below as dos). Consider he following saemens made abou her moion a a paricular ime (marked here in he below diagram). I. Her elociy,, is consan. II. Her y elociy, y, is zero, bu increasing. III. Her acceleraion, a, is zero IV. Her y acceleraion, a y, is zero Which saemen(s) is(are) false? A. I B. II C. III D. IV E. More han one of he aboe F. None of he aboe. y sar C p D p finish here 8. Ruper escapes from a dorm by sliding down rope. As he slides down he rope faser and faser, he becomes frighened and grabs harder on he rope, increasing he ension in he rope. As soon as he upward ension in he rope becomes eual o his weigh... A. Ruper will sop B. Ruper will slow down C. he rope will break D. none of he aboe
9. Romeo hrows a pebble a Julie s window. I bounces off; no harm done. Bluo hrows a brick a Olie Oyl s window. I crashes hrough breaking he window. A. The pebble s force on he window is less han he window s force on he pebble, so no harm is done. B. The brick s force on he window is greaer han he window s force on he brick, so he window breaks. C. Boh of he aboe. D. None of he aboe. 10. Acraeressinhemiddleofhefloorinanoherwise empy an going wes on I-94 a 70 mph. Suddenly a cue fawn jumps ono he road direcly in fron of he an; he drier his he brakes and comes o a sop, missing he fawn. Throughou his process he crae remains a he same spo in he middle of he an s floor. During he braking... 12. Rhonda hrows a seel ball sraigh up. Consider he moion of he ball only afer i has lef her hand bu before i ouches he ground and assume ha forces eered by he air are negligible. For hese condiions, he force(s) acing on he ball is (are): A. a downward force of graiy along wih a seadily decreasing upward force. B. a seadily decreasing upward force from he momen he ball leaes Rhonda s hand unil i reaches is highes poin; on he way down here is a seadily increasing downward force. C. an almos consan downward force of graiy along wih an upward force ha seadily decreases unil he ball reaches is highes poin, afer which here is only he consan downward force of graiy. D. a consan downward force of graiy only. A. he ne force on he crae poins owards he fron of he ruck. B. he ne force on he crae poins owards he back of he ruck. C. he ne force on he crae is zero. 11. Rhonda pulls a bo of mass m across a horizonal surface a a consan elociy, by pulling on a rope wih ension T a an angle θ. Oher forces (W = mg: graiy, N: normal force, f: fricion) also ac in he direcions indicaed. Which of he following relaions among he force magniudes mus be rue? f W N T θ R A. T = f and N = W B. T > f and N > W C. T > f and N = W D. T > f and N < W
The following uesions are worh 10 ps each 13. Consider a coordinae sysem in which he y direcion poins due norh and he direcion poins due eas. The following ecors are gien: a = 10 km 30 norh of due eas b = 5 km 10 souh of due wes c = 2 km due souh Skech (approimaely) each of he aboe ecors and display how all four arrows can be arranged o find d = a+ b c graphically. Resole he ecors ino (,y) componens and calculae a+ b c using he componen forms. Epress he resulan ecor, d, in magniude and direcion form. (Display on your drawing he angle you are reporing.) 14. A long sraigh road in Norh Dakoa sreches for 100 miles in a sraigh line wih occasional sop signs. Saring from res a a sop sign, you accelerae a 1 m/s 2 for 20 seconds, mainain your speed for he ne 60 seconds, and hen hi he brakes (de)acceleraing a 4 m/s 2 unil you are again sopped a a sop sign. Skech a graph of your elociy s. ime. Wha disance separaes he wo sop signs? Coner your answer o miles where 1 mile = 1609 m.
15. In he moie Godzilla s. Terminaor, he Terminaor riding a bike a super human speed is being chased by Godzilla. Tension builds as he pair approach a huge earhuake crack. Boh crack rims are leel bu 20 m apar wih a drop of 10 m. In he scrip he Terminaor bike-sprins o he crack edge and jus barely his he far rim. In he real-world, sunman Ruper decides ha i would be wise o hire a physicis o calculae how fas he mus be going horizonally on he bike o make he crack-jump. Wha is he slowes bike speed ha would resul in a safe landing on he far rim? R 20 m 10 m 16. A spider of mass m = 9 10 5 kg hangs sraigh down on a 30 cm long hread she has jus creaed. Wha is he ension in he hread? A seady breeze from he souh pushes he hanging spider owards he norh so ha he hread makes an angle of 20 wih he erical. Wha is he ension in he hread now? Please draw a free body diagram for each siuaion! graiy 20 30 cm wind m = 9 10 5 kg
17. A large slab (M = 10 kg) sis on fricionless surface. A block (m = 1 kg) ress on op of he slab. The surface beween he slab and he block has a coefficien of saic fricion of µ s = 0.4 and a coefficien of kineic fricion µ k = 0.3. The block is pulled wih a horizonal force T. If T is sufficienly small he block+slab will moe ogeher as one objec; if T is larger, here will be slippage and he block will accelerae faser han he slab (and will eenually be pulled off he slab). A. Draw free body diagrams for each mass separaely. Show and name all forces acing each mass. Show he direcion of he acceleraion (if here is any). B. For each mass separaely and for boh he and y direcions, wrie down he euaions ha follow from Newon s second law (F ne = ma). C. If T = 15 N, here will be slippage. Find he acceleraion of each mass in his case. T fricionless m M µ s =.4 µ k =.3