Physics 101.002         Final         Answers                           Dec. 13, 2007

 

Read each question and its set of answers very carefully.  There is only one best answer for each question.  Don’t be afraid to ask questions of me during the exam.  Just raise your hand if you have one.  Useful information:  g = 32 ft/s2 = 9.8 m/s2.

 

 

1.  The period of pendulum A is 2 s.  The period of pendulum B is 1 s.  Which pendulum is longer in length?

(a) A

(b) B

(c) period is different only because A has the larger mass

 

2.  Both transverse waves and longitudinal waves are capable of producing interference patterns.

(a) True                   

(b) False

 

3.  Sound waves of very low frequency (humans can’t hear) are called

(a) sonic                            

(b) ultrasonic

(c) infrasonic                     

(d) supersonic

 

4.  When successive impulses are applied to a vibrating object in time with the natural frequency of the object

(a) reverberation occurs     

(b) refraction occurs

(c) resonance occurs          

(d) none of the above

 

5.  The second harmonic on a guitar string has twice the speed of the fundamental for that string.

(a) True                   

(b) False

 

6.  You are standing on the earth viewing a partial eclipse of the sun.  In which shadow of the moon are you standing?

(a) the penumbra                

(b) the umbra

(c) the conundrum             

(d) the full

 

7.  A beam of blue light and a beam of red light have exactly the same energy.  Which beam has the smaller number of photons?

(a) red

(b) blue

(c) they both have the same number of photons

 

8.  Green light emitted by excited mercury vapor corresponds to a particular energy transition in the mercury atom.  A more energetic transition might emit

(a) red light                        

(b) blue light

(c) either red or blue light   

(d) white light

 

9.  The color of an opaque object is the same as the color of the light that is

(a) transmitted          

(b) absorbed

(c) reflected                       

(d) all of these

(e) none of these

 

10. A blue light beam and a yellow light beam are aimed at the same spot on a white screen.  What color does the spot appear to be? 

(a) green                            

(b) black

(c) blue                    

(d) yellow

(e) white

 

11. The image in a plane mirror is real because you can see it with the naked eye. 

(a) True                             

(b) False

 

12. Mirages are produced by reflections of light off hot layers of air near the earth's surface. 

(a) True                             

(b) False

 

13. Every body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.  This is a statement of

(a) Newton's first law

(b) Newton's second law

(c) Galileo's "Principia" law

(d) Aristole's law of "De Revolutionibus"

(e) Copernicus' geocentric universe

 

14. How much speed does an object pick up in 2 seconds when it is undergoing a constant acceleration of 2 m/s2 in a straight line?

(a) 2 m/s2

(b) 4 m/s2

(c) 2 m/s   

(d) 4 m/s

 

15. You throw a stone downward.  It leaves your hand with a speed of 10 ft/s.  What is its speed two seconds after leaving your hand?  (Neglect air resistance.)

(a) 10 ft/s

(b) 32 ft/s

(c) 42 ft/s

(d) 64 ft/s

(e) 74 ft/s

 

16. How many Newton's does a 1 kg object weigh? 

(a) 1        

(b) 32      

(c) 16

(d) 9.8     

(e) 19.6

 

17. If the mass of a sliding block is somehow doubled at the same time that the net force on it is doubled, what happens to the resulting acceleration?  It is               it was before.

(a) the same as

(b) twice what

(c) one half what

(d) can’t be determined without knowing what numbers are involved

 

18. Which of the following is an example of Newton's third law? 

(a) the sun has a gravitational attraction for the earth and the earth has a gravitational attraction for the moon

(b) a book setting on a table has the force of gravity "pulling" on it and a contact force "pushing" on it

(c) a woman standing on an elevator exerts a force on the elevator compartment and the compartment exerts a force on the elevator cables

(d) a man standing on a set of scales exerts a force on the scales and the scales exert a force on the man

 

19. Air bags are used in cars to offer you protection during collisions by impeding your motion toward the steering wheel and windshield.  Which of the following is true concerning their use? 

(a) they apply the large force required to stop you

(b) they reduce the impulse necessary to stop you

(c) they increase the time for you to come to a stop

(d) all of the above

(e) none of the above

 

20. You are standing on a frictionless surface of ice.  You throw a 2‑kg object horizontally with a velocity of 20 m/s.  Your mass is 100 kg.  What is your horizontal speed in m/s? 

(a) 20      

(b) 40      

(c) 100

(d) 0.20   

(e) 0.40

 

21. If you push on an immovable wall for an hour, is there any work done on the wall?

(a) Yes                     

(b) No

 

22. Which is more powerful?

(a) an engine that does 1000 ftilb of work in 1 second

(b) an engine that does 1000 ftilb in 1.5 seconds

(c) one is just as powerful as the other since they can do the same amount of work

 

23. Doubling one's velocity only doubles one's danger.

(a) True                   

(b) False

 

24. An object of mass 6 kg is traveling at a velocity of 30 m/s.  How much work was required to obtain this velocity starting from a position of rest?

(a) 180 Joules           

(b) 36 Joules

(c) 2700 Joules                  

(d) 5 Joules

(e) 180 N

 

25. Which energy is an energy of position?

(a) kinetic                          

(b) heat

(c) potential                       

(d) force x time

(e) watts

 

26. Can a body have momentum without having energy?

(a) Yes                     

(b) No

 

27. A car moving initially at 50 kilometers/hour skids with locked brakes to a stop in 10 meters.  How far in meters will the car skid to a stop with locked brakes if it is traveling at 200 kilometers/hour?

(a) 20                       

(b) 60

(c) 90                       

(d) 120

(e) 160

 

28. If I have a 100% efficient machine which lifts weights, how much energy must be supplied to it to lift a 2000 lb weight 3 ft?

(a) 6660 ftilb           

(b) 2000 lb

(c) 6000 hp                        

(d) 6000 ftilb

 

29. How does a long pole help a tightrope walker to balance himself?

(a) the pole increases his torque

(b) the pole can be rotated rapidly to achieve balance

(c) it doesn't help

(d) the pole increases his rotational inertia

(e) the pole makes the man heavier

 

30. Two kids are sitting on a seesaw as shown.  If the kid on the left weighs 75 lb, what must the kid on the right weigh in order to balance the seesaw?

(a) 50 lb

(b) 75 lb

(c) 100 lb

(d) 150 lb

(e) 200 lb

 

31. The center of mass of a pole vaulter can actually pass under the bar as the pole vaulter passes over the bar.

(a) True                   

(b) False

 

32. A person with his back to a wall cannot bend down to touch his toes with his hands without bending his knees.  Why?

(a) his center of mass would move beyond his area of support and he would fall

(b) angular momentum would not be conserved

(c) he can't develop the appropriate torque

(d) he is in neutral equilibrium

 

33. In class a metronome was used to discuss rotational inertia.  When the sliding mass of the metronome was placed as far from the pivot as possible, the period of the pendulum              because the rotational inertia of the pendulum             .

(a) decreased, decreased    

(b) decreased, increased

(c) increased, increased      

(d) increased, decreased

 

34. The object below is traveling in a circle at constant speed.  What is the direction of the acceleration of the object?

(a) tangent to the circle

(b) between tangent to the circle and perpendicular to the circle

(c) toward the center of the circle

(d) away from the center of the circle

(e) there is no acceleration

 

35. You and a friend are riding on a playground merry‑go‑round.  When you try to roll a ball to your friend you notice that it curves.  You report that a force caused this curving.  What is the name of that force?

(a) centripetal           

(b) circular

(c) centrifugal           

(d) normal

(e) coriolis

 

36. In shooting a rubber band one needs to                       in order to shoot the rubber band farther.

(a) stretch the band as tight as one can

(b) fire it faster

(c) warm the rubber band before shooting

(d) put spin on the rubber band

(e) take longer in the firing of the rubber band

 

37. What is required to change the angular momentum of a system?

(a) a force                          

(b) a spin

(c) a jerk                            

(d) a torque

(e) an impulse

 

38. When an ice skater spins with arms outstretched and pulls them inward, the speed at which she spins increases.  Does her angular momentum increase?

(a) Yes                     

(b) No

 

39. The non-spinning person below is holding a spinning bicycle wheel with its spin "up."  The person is standing on a platform that is free to rotate.  What happens when the person flips the bicycle wheel over?

(a) nothing

(b) he starts to spin with spin "down"

(c) he starts to spin with spin "up"

(d) the wheel stops spinning

 

 

 

40. If somehow the moon were moved to a distance twice as far away from the earth as it is now, the force that the earth has for the moon would

(a) be twice what it is now

(b) be one half of what it is now

(c) be four times greater than it is now

(d) be one fourth as much as it is now