PHYSICS 11 1 EXAM 3

FALL 2006

In all problems please ignore the effects of friction.

37. What must be the mathematical form of the force needed to produce simple harmonic motion? Hint: k is a constant

38. A point mass of 5.0 kg vibrates on the end of a horizontal massless spring between points A. and B. as shown in the figure to the right. The spring constant is 90 Nlm. What is the speed of the mass 0.20 m from the equilibrium point?

(a) 1.1 mls m ( c ) 2.6 rnls (d) 3.4 rnls (e) 4.2 mls

39. A sound wave traveling in air in the x direction at room temperature is described by x = 40. cos (20. t). What is the wavelength of this sound wave.

(a) 20 m (b) 40 m (c) 65 m (d) 82 rn633

40. Which waves are purely longitudinal? 0 sound waves in air (b) infra red waves in air from the sun (c) light waves in a vacuum (d) waves on a plucked guitar string (e) surface waves in a shallow pan of water

41. A guitar string with a mass of 4.0 g and a length of 50. cm is

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vibrating in it% second harmonic and produces a sound with a frequency of 700. Hz. What is the tension in the string?

(a) 240 N (b) 380 N (c) 520 N (d) 760 N (e) 980 0 42. On a busy street corner you hear sound with an intensity level

of 80 decibels. What is the intensity of the sound?

(a) I o - ~ w1m2 (b) I 0" w1m2 (c) 1 o6 w/m2 (e) I 0" w/m2

43. An organ pipe 50.0 cm long and closed at one end sounds it's third harmonic. What is the frequency of the sound produced?

(a) 340 ~ z 6 ) 5 1 0 3 (c) 680 Hz (d) 750 Hz (e) 890 Hz

44. You are traveling east on a 2-lane highway at 20.0 rnls. A police car is traveling west on the same highway at 20.0 rnls and sounds it's siren. The policeman hears a frequency of 600. Hz. What frequency do you hear for the policeman's siren?

(a) 533 Hz (b) 600 Hz (c) 639 H G K @ ( ~ ) 690 Hz

45. In a hydraulic system the force is applied to a hose 1 cm in diameter. This is connected to a piston 40 cm in diameter that applies the force to the object to be lifted. What force must you apply to lift a weight of 5000 N?

(a) 1.8 N G K 9 (c) 4.6 N (d) 5.3 N (e) 6.8 N

46. A 55 gram piece of iron is floating in a pool of mercury. What is the buoyant force on the iron?

(a) 0.38 N (b) 0.44 N@FM-(~) 0.63 N (e) 0.75 N

47. In Bernoulli's equation what does the term % p vI2 represent?

(a) the gravitational potential energy (b) the gravitational potential energy per unit fluid volume (c) the kinetic energy

the kinetic energy per unit fluid volume (e) the work

48. In a lecture demonstration two ping pong balls were suspended by threads as shown in the figure to the right. The lecturer directed a stream of air at point - which resulted in the balls -

(a) A, being attracted to each other (b) A, being forced apart mB, being attracted to each other (d) B, remaining motionless (e) B, being forced apart

Water is flowing in a tube shown to the right. The tube has a diameter of 5.0 cm at point A and 2.0 cm at point B. The velocity of the water at point A is 8.0 mls. What is the difference in pressure between points A and B? Hint: First find velocity at point 6.

a) 1 . 2 x 1 0 ~ ~ a (b) 1 . 6 ~ IO 'P~ (c )2 .0x106~a (d)2.5x106pa GzG?

50. A steel can has an inside volume of 0.50 m3 and is completely filled with water on a cool day when the temperature is 10 CO. If the temperature then rises to 30 CO, what volume of water spills out of the can? Neglect the effects of evaporation of the water.

<-a(c) 0.0021 m3 (a) no water spills out b 0.001 7 (d) 0.0025 m3 (e) 0.0032 m

A balloon is filled at room temperature (20.0 CO) with helium (He). The volume of the filled balloon is 0.0850 m3. Use this to answer questions 51. and 52.

51 . How many moles of helium are in the balloon? Hint: One mole of mono-atomic He has a mass of 4.0 xlom3 kg.

&-3 (b) 4.8 moles (c) 7.3 moles (d) 1 6 moles (e) 52 moles

52. What is the RMS velocity of the helium in the above balloon?

(a 460 rnls (b) 580 rnls (c) 720 mls (d) 950 rnls dmmiEs) 53. At room temperature (20 CO) a minimum pressure of - IS

required to liquefy C02. As the pressure is increased a - temperature is needed to boil liquid C02.

(b) 5.2 atm., higher (c) 56 atm., lower (e) 73 atm,. higher

54. On a nice fall day in Iowa the temperature was 50 F0 and the partial pressure of water vapor in the air was measured to be 0.50~1 o3 Pa. What was the relative humidity?

m ( b ) 50 % (c) 58 % (d) 65% (e) 72 %