PHYSICS 1210 Exam 2 University of Wyoming 14 March ( Day!) points

Size: px

Start display at page:

Download "PHYSICS 1210 Exam 2 University of Wyoming 14 March ( Day!) points"

Felicity Watkins
5 years ago
Views:

1 PHYSICS 1210 Exam 2 Univesity of Wyoming 14 Mach ( Day!) points This test is open-note and closed-book. Calculatos ae pemitted but computes ae not. No collaboation, consultation, o communication with othe people (othe than the administato) is allowed by any means, including but not limited to vebal, witten, o electonic methods. Shaing of mateials including calculatos is pohibited. If you have a question about the test, please aise you hand. Please do not open this test booklet until eveyone has eceived a booklet and the test administato has indicated fo you to begin. While you ae waiting, make sue that you name is witten clealy at the top of the fist page. g = 9.80 m/s 2 1 adian = mi = km 1 m = in = 3.28 ft v A B v = ABcos = A x B x + A y B y + A z B z v = d v dt a v = dv dt = d 2 v dt 2 v x = v 0x + a x dt v = v 0 + a v t v x = v 0x + a x t v x = x 0 + v x dt = v 0 + v v 0 t a t 2 x = x 0 + v 0x t + 1/2 a x t 2 v 2 x = v 2 0x + 2a x (x x 0 ) x x 0 = (v 0x + v x ) t/2 x = (v 0 cos 0 ) t y = (v 0 sin 0 ) t 1/2 g t 2 v x = v 0 cos 0 v y = v 0 sin 0 g t R = v 2 0 sin(2 0 )/g a = v 2 /R a = 4 2 R/T 2 v T = 2 R/T v P/A = v P/B + v B/A W = F d 2 s = Fl cos( ) K = 1 mv 2 W 2 tot = K 1 U 0 + K 0 + W nc = U f + K f p = mv t J = 2 F dt = p t v v 1 cm = m i i m i p cm = m i v i m i = p F el = kx U el = 1 kx 2 2 totally inelastic collision: v f = (m 1 v 10 + m 2 v 20 )/(m 1 + m 2 ) ( m1 m2 ) v10 + 2m2v20 ( m2 m1 ) v20 + 2m1v10 elastic collision: v1 f = ; v2 f = m1 + m2 m1 + m2 P = dw dt P net = F v = a p A

Name: 1. (6 points) A pofesso swings a ubbe stoppe in a hoizontal cicle on a sting in font of his class. He eleases the sting when the stoppe is ight in font of Kelsey, who sits in the font ow.

2 Name: 1. (6 points) A pofesso swings a ubbe stoppe in a hoizontal cicle on a sting in font of his class. He eleases the sting when the stoppe is ight in font of Kelsey, who sits in the font ow. Will the stoppe hit Kelsey? a. Yes. b. No. c. It will if the stoppe is moving fast enough. 2. (10 points) A 20-kg stone feels a geate pull due to the eath s gavity than a 10-kg stone. Howeve, if you dop them, they fall with the same acceleation. Why? 3. (6 points) High-speed motion pictues of the takeoff of a jumping 210-µg flea yielded the data to plot the flea s acceleation as a function of time as shown. How does the maximum net foce on the flea compae to its weight? a. The net foce is about equal to the flea s weight. b. The net foce is about 14 times the flea s weight. c. The net foce is about 62 times the flea s weight. d. The net foce is about100 times the flea s weight. e. The net foce is about 140 times the flea s weight. 4. (8 points) Imagine that you ae holding a book weighing 4 N at est on the palm of you hand. Complete the following sentences: a. A downwad foce of magnitude 4 N is exeted on the book by. b. An upwad foce of 4 N is exeted on by you hand. c. The Newton s thid law eaction to the foce in pat a is a foce of magnitude, exeted on by. d. The Newton s thid law eaction to the foce in pat b is a foce of magnitude, exeted on by. PHYS Exam 2 A 1 of 7

3 5. (6 points) You swing a ball on the end of a lightweight sting in a hoizontal cicle at a constant height and constant speed. Can the sting itself eve be tuly hoizontal? a. No, the sting can only be below hoizontal. b. Yes, the sting may be tuly hoizontal. c. Yes, the sting may be hoizontal o even above. 6. (8 points) A pendulum on a fictionless pivot dops fom its maximum displacement and falls without dag to its lowest position. Indicate whethe the statements below ae always tue (T), sometimes tue (S), o always false (F). T S F The pendulum s mechanical enegy is constant duing this pocess. T S F The pendulum s kinetic enegy is constant duing this pocess. T S F The pendulum s potential enegy is constant duing this pocess. T S F The pendulum s momentum is constant duing this pocess. 7. (8 points) A Vogon s gandmothe floats at a constant velocity though space. The Ravenous Bugblatte Beast of Taal also floats at a diffeent constant velocity though space until they meet. The beast of couse immediately eats he, and continues to float though space. Indicate whethe each statement below is always tue (T), sometimes tue (S), o always false (F). T S F The velocity of thei cente of mass is constant duing this pocess. T S F Thei total kinetic enegy is constant duing this pocess. T S F Thei total momentum is constant duing this pocess. T S F The beast s velocity is constant duing this pocess. PHYS Exam 2 A 2 of 7

4 8. (10 points) The diagam shown appoximates the potential enegy of two hydogen atoms whose electons ae aligned in opposite oientations. The hoizontal axis (xvaiable) is the distance between the nuclei of the two atoms. The vetical axis is the potential enegy of the system. Seveal positions (x A, x B, etc.) ae indicated. Enegy U 0 0 x A x C x D x E distance x x B a. What is the diection of the foce between the atoms at position x A? pulling them togethe no foce pushing them apat b. What is the diection of the foce between the atoms at position x B? pulling them togethe no foce pushing them apat c. What is the diection of the foce between the atoms at position x C? pulling them togethe no foce pushing them apat d. What is the diection of the foce between the atoms at position x D? pulling them togethe no foce pushing them apat e. What is the diection of the foce between the atoms at position x E? pulling them togethe no foce pushing them apat 9. (6 points) An elevato is loweed at a constant speed. The wok done on the elevato by the cable holding it up is a. negative. b. zeo. c. positive. 10. (7 points) A sping has a sping constant k = 50 N/cm. How much wok is equied to stetch o compess it 25 cm fom its est length? a J. b J. c. 2.0 J. d. 4.0 J. e J. f J. g J. h J. PHYS Exam 2 A 3 of 7

5 11. A man dags a cate of mass m up a amp by pulling it with a stap. The amp is inclined at an angle of above the hoizontal, and the stap is inclined at an angle of above the amp. The coefficient of kinetic fiction between the cate and amp is µ k, and the man pulls on the stap with a foce of magnitude F. F +y +x a. (6 points) The foces acting on the cate ae its weight mg, the foce F fom the stap, the nomal foce N fom the amp, and fiction f. Daw a fee-body diagam fo the cate including all of these foces. Make sue thei diections ae coect. b. (10 points) Complete the table below with the x- and y-components of the diffeent foces acting on the cate and of the net foce on the cate. Use the inclined x and y diections illustated in the diagam above. Expess all components in tems of one o moe of the quantities,, m, F, and g. m g F N f F x-component y-component PHYS Exam 2 A 4 of 7

6 c. (5 points) Indicate whethe the magnitude of the foce of fiction f inceases (+), deceases (_), o emains unchanged (0) unde each of the following changes to the system. + _ 0 The angle inceases. + _ 0 The angle inceases. + _ 0 The magnitude of the pulling foce F inceases. + _ 0 The cate s mass m inceases. + _ 0 The magnitude of the gavitational field g inceases (if it could). d. (5 points) Suppose that the cate s mass m = 45 kg, the incline of the amp = 20, the angle of the stap above the amp = 30, and the coefficient of fiction µ k = What is the lagest magnitude of the pulling foce F that will not lift the cate off the amp? (O, the smallest magnitude of F that will lift the cate off the amp?) (Hint: That would make F y > 0 with N = 0.) PHYS Exam 2 A 5 of 7

7 12. (24 points) I swing a 100-g toy on a 0.50-m sting in a cicle in a vetical plane. (Its axis of otation is hoizontal.) The toy moves with constant mechanical enegy (K + U g ), and the speed of the toy is 2.00 m/s at the top of the cicle. Fo each position (1, 2, and 3) indicated on the diagam, a. Tell me the kinetic enegy of the toy. (Hint: What quantity is conseved?) b. Tell me the speed of the toy. 2 c. Daw a fee-body diagam fo the toy. d. Find the x- and y-components of the toy s acceleation, accoding to the axes shown. e. Find the magnitude of the tension in the sting y +x PHYS Exam 2 A 6 of 7

8 13. A lab ail-cat with a mass of kg tavels with an initial speed of m/s towad a stationay ail cat with a mass of kg. When the two cats collide, the collision tigges one cat s sping bumpe, pushing them apat. Afte the collision, the kg cat has a speed of m/s. a. (15 points) What is the velocity (speed and diection) of the kg cat afte the collision? b. (10 points) How much wok did the sping do on the cats? In othe wods, how much kinetic enegy did the sping add to the two cats? PHYS Exam 2 A 7 of 7

PHYSICS 1050 Mid-term Test 1 University of Wyoming 8 February 2007

PHYSICS 1050 Mid-term Test 1 University of Wyoming 8 February 2007 Name: PHYSICS 1050 Mid-tem Test 1 Univesity of Wyoming 8 Febuay 2007 This test is open-note and open-book. This means that any efeence mateial is pemitted duing the test. Calculatos also ae pemitted. Howeve,