PHYS 1110 Final NAME:______________________________

Fall 2008 F.1 Final

Student ID #__________________________________________________ Section number and TA Name:___________________________________

Exam Version 0001

Please do not open the exam until you are asked to. • Your exam should have 12 pages, numbered F.1 thru F.12. • This exam consists of 30 multiple choice questions, worth 3.33 points each.

PLEASE!!

1. Print your name on each page in the space provided. 2. Print your student Identification Number on the page above. 3. Bubble your name, ID, and exam version number on the bubble sheet provided (exam version number

field is next to the date and just labeled 1234). By handing in this exam, you agree to the following statement: "On my honor, as a University of Colorado Student, I have neither given nor received unauthorized assistance on this work"

Signature______________________________________________

Possibly useful information: On any problems involving gravity, use g=9.8 m/s2!

You may also find it useful to know sin 30°=0.5, cos 30°=0.866, tan 30°=0.577, and for

ax2 + bx + c = 0, x = -b ± b2 - 4ac2a

.

Neglect air resistance (unless stated otherwise). For some problems, extra (unneeded) information is given!

Circle the closest answer and Bubble in questions 1-30 ON YOUR BUBBLE SHEET! Some constants which might prove useful: Mass of Earth: 5.98 x 1024 kg Radius of Earth: 6.38 x 106 m Gravitational constant G = 6.67 x 10-11 Nm2/kg2

Density of water: 1 g/cm3 = 1000 kg/m3

Atmospheric pressure: 1 atm = 105 Pa = 14.7 psi = 760 mmHg Moment of inertia for objects with mass M and radius R: Ring or hoop with axis through center: MR2

Cylinder or disk with axis through center: 1/2 MR2

Solid sphere with axis through center: 2/5 MR2

Hollow sphere with axis through center: 2/3 MR2

Rod of full length L with axis through center: 1/12 ML2

Rod of full length L with axis at one end: 1/3 ML2

PHYS 1110 Final NAME:______________________________

Fall 2008 F.2 Final

1. A 15 kg rock is 1.2 x 108 m from the center of a planet with a mass of 7.0 x 1026 kg. What force does the rock exert on the planet? A) 3.2 N B) 27 N C) 49 N D) 147 N E) 5.9 x 109 N

2. A solid piece of plastic of volume Vp, and density ρp is floating in a cup of water with density ρw. What is the magnitude of the buoyant force on the plastic? A) 0 B) ρw Vp

C) ρp Vp D) ρw Vp g E) ρp Vp g 3. The velocity vectors are shown at an early time (v1) and a later time (v2). Which vector could represent the average acceleration during this time?

1vr 2vrA) A B) B C) C D) D E) None of them (A) (B) (C) (D)

PHYS 1110 Final NAME:______________________________

Fall 2008 F.3 Final

4. A mass m is on the end of a spring and is oscillating back and forth between –A and A as shown in the figure. When the mass is at position 0 and moving to the right, the acceleration of the mass is

x m

k -A +A 0

A) Positive (to the right) B) Negative (to the left) C) Zero D) Impossible to determine 5. A rope is looped over a pulley and connected to a bucket of water. The bucket has a mass of 25 kg and is being lowered at a constant speed. The rope which the person is lowering makes an angle of 30° with respect to the horizontal direction as shown. What is the force the person is exerting on the rope?

30°

A) 0 N B) 123 N C) 245 N D) 490 N E) Impossible to determine with the information given 6. Two air carts are initially at rest on parallel tracks. Cart A has twice the mass of cart B. The same force is applied to both carts for the same amount of time. After that time what can we say about the magnitude of the momenta of the two carts? A) Cart A has the same momentum as Cart B B) Cart A has twice as much momentum as Cart B C) Cart B has twice as much momentum as Cart A D) Cart A has more momentum but it is not twice as much E) Cart B has more momentum but it is not twice as much

PHYS 1110 Final NAME:______________________________

Fall 2008 F.4 Final

7. Three tanks are filled to the same height with water as shown. The diagrams are correctly scaled. For which tank is the pressure on the bottom the greatest? A) A B) B C) C D) Exactly two tanks are tied E) All three tanks are tied 8. A 12.0 kg mass is on the end of a horizontal spring with a spring constant of 85 N/m. The mass is initially at the equilibrium position with a speed of 4.0 m/s. How far out will the mass go before returning?

x m

k -A +A 0

A) 0 m B) 0.8 m C) 1.5 m D) 2.3 m E) None of the above 9. An elevator car is at rest when its supporting cable breaks. The elevator car falls a distance H before first making contact with a spring. The spring is compressed by an amount L before the elevator comes to rest. At what point during the fall does the elevator start to slow down (remember to ignore air resistance)?

Elevator car

A) Before the elevator first touches the springB) At the exact instant the elevator touches the springC) After the elevator first touches the spring D) More than one of A,B,C is a possibility, need more information.

Elevator car

H

L

PHYS 1110 Final NAME:______________________________

Fall 2008 F.5 Final

10. A Ferris Wheel has a diameter of 40 m. How fast would the Ferris Wheel have to rotate for a person to feel weightless at the top? A) Need more information to solve this problem B) 0.5 rad/s C) 0.7 rad/s D) 14 rad/s E) 20 rad/s 11. The graph shows the position of two trains on parallel tracks as a function of time. Which of the following statements is true?

time

position train A train BA) Both trains speed up the entire time B) At time tC both trains have the same speed C) Both trains have the same velocity at some point before tC. D) Both trains have the same acceleration at some point before tC.

tCE) 0 or 2 of the above answers are correct 12. A ruler has had a hole drilled through the middle and this hole is a pivot around which the ruler can freely rotate. The ruler has a mass of 0.2 kg and a length of 1 m and is initially at rest. The stand on which the ruler is mounted is securely fastened to a table. A student briefly pushes downward on the right side of the ruler (50 cm from the middle) with a force of 9.8 N causing the ruler to start spinning clockwise. What can you conclude about the net force on the ruler and net torque (around the pivot) on the ruler during the time the student is pushing? A) Net force = 0 and net torque out of the page B) Net force = 0 and net torque into the page C) Net force ≠ 0 and net torque = 0 D) Net force ≠ 0 and net torque out of the page E) Net force ≠ 0 and net torque into the page

PHYS 1110 Final NAME:______________________________

Fall 2008 F.6 Final

13. A rock is shot from a large cannon on the Earth and streaks out to space. At the moment that it crosses the orbit of the International Space Station (ISS), what is the magnitude of the acceleration of the rock compared to the acceleration of the International Space Station? Ignore any gravitational forces between the ISS and the rock.

ISS

EarthA) Rock’s acceleration is smaller rockB) Rock’s acceleration is greater C) Accelerations are the same D) Depends on the relative masses of the rock and ISS E) Depends on the initial launch velocity of the rock 14. A force F of 3.0 N is applied to a wrench as shown. The force is applied 0.50 m from the pivot at the angle shown. The vector torque is A) 0.75 N m into the page 0.5 m B) 0.75 N m out of the page C) 1.3 N m into the page D) 1.3 N m out of the page E) None of these 15. A hockey puck slides down into and through the bottom of a smooth icy ditch, as shown. (The path of the puck is shown with the dashed line.) Assume no friction and assume that the bottom of the ditch has a round circular shape. At the moment when the puck is at the bottom of the ditch, which free-body diagram most accurately represents the directions and relative magnitudes of the forces on the puck.

A) B) C) D) E)

60º

F

PHYS 1110 Final NAME:______________________________

Fall 2008 F.7 Final

16. A kid throws a rock off of the top of a cliff with a speed of 16 m/s at an angle of 30o with respect to the horizontal. It reaches the ground after 3.5 seconds. How tall is the cliff? A) 4 m B) 12 m C) 28 m D) 32 m E) 60 m

17. At t = 0, a rock is thrown straight up from the surface of the earth with a speed of a few meters per second. It rises and then falls back down to the ground. Assume that air resistance is negligible. Upward is chosen as the positive y-direction. Which of the following graphs most accurately shows velocity vs. time for the rock while it is in flight? 18. An astronaut in space is “weighed” by connecting the astronaut to the end of a spring (with a spring constant of 750 N/m) and measuring the period. If the period is measured to be 2.0 s, what is the mass of the astronaut?

t

v

t

v (a) (c)

t

v (b)

t

v (d) (e) None of these is correct.

A) 19 kg B) 55 kg C) 76 kg D) 188 kg E) None of the above

PHYS 1110 Final NAME:______________________________

Fa

19. A mass is hanging from a rope and swinging around a circular path at constant speed as shown in the figure. Which answer shows the forces acting on the mass (neglecting air resistance)?

Support

rope circular path

mass

B. A.

D. .

20UinABCDE) 21sastABCD

C

ll 2008 F.8 Final

E. None of these

. A hockey player takes a shot on an empty net using a 0.30 kg puck from deep in his own zone. nfortunately he is playing on really bad ice so the coefficient of kinetic friction is 0.20. What is the minimum itial speed the puck needs to have to make it the 22 m to the goal? ) 4.2 m/s ) 6.7 m/s ) 9.3 m/s ) 21 m/s 86 m/s

. Suppose a ping-pong ball (mass 5 g) and a bowling ball (mass 5 kg) are rolling toward you. Both have the me momentum, and you exert the same force to stop each. During the period in which they are being opped, which ball travels farther? ) ping-pong ball ) bowling ball ) both travel the same distance ) impossible to determine

PHYS 1110 Final NAME:______________________________

Fall 2008 F.9 Final

22. Air cart A has a mass of 0.4 kg and a speed of 2.0 m/s. It strikes air cart B which has a mass of 0.6 kg and is at rest. The two air carts stick together and move off. How much energy is lost in the collision? A) 0.32 J B) 0.48 J C) 0.61 J D) 0.67 J E) 0.80 J 23. A block and sphere are connected by an ideal string (massless, not stretchy) running over an ideal pulley. There is no friction between the block and the table, and we can neglect air resistance.

Block

Sphere A

Massless, frictionless pulley

Floor

Sph

Table

When the block is released, what is the motion of the sphere?

with frictionNo friction A) The sphere accelerates downward at a constant 9.8 m/s2

B) The sphere accelerates downward at a > 9.8 m/s2 and the acceleration is constant in time. C) The sphere accelerates downward with a < 9.8 m/s2, and the magnitude of this acceleration changes steadily with time D) The sphere accelerates downward with a < 9.8 m/s2, and the acceleration is constant in time. E) The sphere acceleration gradually increases from 0 to 9.8 m/s2.

PHYS 1110 Final NAME:______________________________

Fall 2008 F.10 Final

A hoop and a sphere roll without slipping and an ice cube slides without friction. They are all released from rest at the top of a long ramp. They all start at the same height, h, above ground level. 24. When the three objects are down at the flat part at the bottom, which one is moving the fastest?

Start

h

A) The hoop. B) The sphere. C) The ice cube. D) The sphere and hoop tie for fastest, beating the ice cube. E) They all have the same speed. 25. In the previous problem, after leveling out at the bottom, the track climbs up again on the right as shown in the figure. Which object ends up the highest on the right side? A) The hoop. B) The sphere. C) The ice cube. D) The sphere and hoop stop at the same height, which is higher than where the ice cube gets to. E) They all stop at the same height. 26. A pottery wheel (disk) of mass 20 kg and radius 15 cm is initially at rest. A piece of clay with a mass of 4 kg and a speed of 10 m/s hits the side of the pottery wheel as shown. The clay sticks to the outside of the wheel causing the wheel to start rotating. After the collision, what is the angular velocity of the wheel? Note that the center of the pottery wheel is fixed in place. RA) 6 rad/s B) 11 rad/s C) 19 rad/sD) 27 rad/sE) 67 rad/s

PHYS 1110 Final NAME:______________________________

Fall 2008 F.11 Final

27. A jar is filled with liquid of uniform density. The liquid is flowing out of the exit at point D with constant velocity. Points B and C are at the same height as point D. Point A is at the top of the jar. Rank the pressures at the four points from highest to lowest.

A

A) A>B=C=D B) B>A=C=D C) D>C>B>A D) B>C>A=D E) Need more information to rank all of them. 28. A disk with a mass of 470 g and radius of 12 cm is spinning on a frictionless pivot at 60 revolutions per minute. A finger is pushed against the edge of the disk in the direction of the center of the disk with a force of 0.7 N. The coefficient of kinetic friction between the finger and disk is 0.40. What is the magnitude of the angular acceleration? A) 0.1 rad/s2

B) 4.7 rad/s2

C) 6.3 rad/s2

D) 9.9 rad/s2

E) 25 rad/s2

N 7.0=Fcm 12=r N 7.0=Fcm 12=r

CB D

PHYS 1110 Final NAME:______________________________

Fall 2008 F.12 Final

29. If you stood on a planet which has a mass that is twice as great as the Earth’s and a diameter which is also twice as great, you would weigh A) ¼ of your Earth weight B) ½ of your Earth weight C) the same as on Earth D) twice your Earth weight E) four times your Earth weight 30. A 3 m long plank has a mass of 25 kg and a pivot in the middle. A 55 kg person stands on the left end of the plank. How far from this person (x) should a 65 kg person stand to balance the plank?

xA) 0.23 m B) 1.85 m C) 2.54 m D) 2.77 m E) There is no way for this to happen