Spring+07+Exam+2.pdf

Pnysrcs 2750 - WrNrBn 2007 - Ex.r.rr # 2B N,q.NrB:

:Lt tName: /'' '4 f .n,t J * I '-

Student #:

enter the first letterof last name in the box:

Have your student ID displayed on the desk.

Write your name in every problem page and sign this page.

The only items you may have on your desk during the examination are: your copy of the

examination, your own handwritten formula sheet, a calculator, pencils and pens and

an eraser.

You must tum in your signed formula sheet at the end of the exam. If you need to use

scratch paper, use the back of your examination. Do not store formulas in your

calculator.

Show all of your work on your examination paper.

EXCEPT FOR MULTIPLE CHOICE QUESTIONS, ANY ANSWER PRESENTED

WITHOUT JUSTIFICATION, WHETHER CORRECT OR NOT, WILL LIKELY

EARN NO CREDIT.

If something is not clear to you ASK NOW.

When you have finished the exam, turn it in and you may leave. Once you have left the

room you will not be allowed to return to resume work.

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submit only his/her work for evaluation. It is the explicit policy of this Department to act

upon every case of academic dishonesty.

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Pnvsrcs 2750 - Wnrnn2007 - Exau # 2B N,q,rdr: ul'il"f . ,'r i",'-;,---

Questions

l. (5 points) A block rests on an incline that forms an angle 0 with the horizontal. If the

coefficient of static friction between the block and the surface of the slide is p.=1 what is the

largest value of 0 for which the block does not slide? ,! .,t.0{,.-.,.. -^.,t . i ,tl;:

i' a.450 j b. 600 c. loo d. 3oo , t'

e. carhomnsWdi without knowing the mass of the block

2. (5 points) The horizontal sudace on which the objects shown in the figure slide is frictionless.The tension in string 2 is 4 N. Determine F.

a.30N b.25 N c.35N e.20N

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3. (5 points) A 70-kg man stands on a bathroom scale in an elevator. Which of the followingnumbers most closely approximates what the scale reads if the elevator is ascending withan acceleration of 3.0 m/s2?

.. -'\,a.690N I b.900N 'r c.480N

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d. 1050 N e. 140 N

\"\-..-*---./-".(5 points) Which force is responsible for holding a car in an unbanked curve?

a. the vertical component of the normal forceb. the force of frictionc. t-Ilqfltoizontal component of the normal force

'$dh. car's weig'h!€...t-hereaction force to the car's weight

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Pnvslcs 2750 - WmrBn2007 - Exau # 2B N.rvrn:

5. (5 points) Which force is responsible for holding a car in a frictionless banked curve?

a. the horizontal component of the normal force -'1

U. ilie vertical component of the car's weight' ' ' i, ) -, iic. the reaction force to the car's weight ,* r'it.*'

d. the horizontal component of the Jar's weigh, i:r,r."! '' "''

e. the vertical component of the normal force

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6. (5 points) A 50-Kg boy runs at a speed of l0 m/s and jumps on a cart that is initially at rest. Ifthe speed of the cart with the boy is 2.5 m/s, T.!.at is the mass of the cart?

a. 210 Kg b.260 Kg ' c. 150 Kg I d. 300 Kg e. 175

7. (5 points) A large bus collides with a sub-compact car. During the time the two are colliding.'.

a. the bus exerts a force on the car but the car does not exert a force on the bus.

b. the bus exerts a greater amount of force on the car than the car exerts on the bus'

c. the car exerts a g-reater amount of force on the bus than the bus exerts on the car.

frF-ejgs*'o'ts-6 'esrs lnesll o-t,totqe-gr-!\e cs aslhe,carff:f ;L*:3lf;1. ,"e. neither exerts a force on the other, the car gets smi

the way of the bus.

8. (5 points) A 3.0-N force acts horizontally on a 1-Kg block that is initially at rest on a

horizontal surface. The coefficient of static friction between the block and the surface is 0.40.

What is the magnitude of the frictional force that acts gn 1ne j"lfk?

\-'a.8N b.5N c.3N dF"N e.2N

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PHvslcs 2750 WtNrBn2DAT - Ex.lna # 2B Navrp: {YWt# -

Problem I [20 points'l

The two blocks shown in the figure are connected by a massless string and slide on frictionless

surfaces.

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(a) (5 points) Draw a diagram showing all the forces that act on each block.

+Ys(b) (5 points) What is the acceleration of the right block, and in what direction?

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equilibrium (no sliding un or dow2X

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Pnysrcs 2750 - Wrnrrn2007 - Exau # ZB

Problem 2 [20 points]

A 4.0-kg mass (B) initially at rest on a horizontal frictionless surface, is struck by a2.0-kgmass (A) moving along the x axis with a speed of 8.0 m/s. After the collision, mass A has aspeed of 4.0 m/s at an angle of 600 from the positive x -axis. The two masses do NOZ sticktogether.

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(a) (5 points) What is the x-component of the velocity of mass B after the collision?

tc(c) (5 points) What is the speed of mass B after the collision?

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(d) (5 points) In what direction does B move after the collision (give the angle between thevelocity and the.r-axis)

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Pnvsrcs 2754 - WrNrnn 2007 - Ex.twr # 28 Na.un: ,gf#,*'' {$x/'Problem 3 [20 pointsl

A 0.1-kg toy airplane is tied to the ceiling with a string and moves with a constant speed of 3

m/s in a horizontal circle of radius 0.5 m as illustrated in the figure.

(a) (5 points) Draw a diagram of the forces acting on the toy airplane.

(c) (5 points) Find the angle the string forms with the-v..-ertical.

(d) (5points) Find the tension in the string.

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