SAMPLE FINAL EXAMINATION FROM AU’ 11, FOR AU12.

1.  (40 POINTS) In a Chabot College  physics lab experiment, a piece of balsa wood is completely submerged under the water. The wood is  at rest  and is tethered  by a string to the bottom of a container of  water. The balsa wood has volume is 1.34x10 -6 m3  and density of 0.16 x10 3 kg/m3.  Water, on the other hand,  has density  1.00x103 kg/m3.  Answer the following questions and show all work and reasoning.

(a)   (6 points)  What is the direction of the buoyant force acting on  the wood, up or down ? Circle  up”  or  “down.”
(b)   (6 points)  What is the direction of the tension force acting on the wood, up or down ? Circle  up”  or  “down.”  ?  
(c)   (6 points)   What is the direction of the force of gravity acting on the wood, up or down ? Circle  up”  or  “down.”   ?
(d)   (22 points) What is the magnitude T of the tension in the string?

 

 

 

 

 

 

 

 

 

 

 

 


2. (18 POINTS)  You are a medical professional attempting to explore the problem of blood pressure drops in diseased,  narrowed arteries. The arteries have  approximately circular cross-section.

In a  section of an artery, the diameter d1 is 0.0050 m and the speed v1 of the blood is 0.500 m/s.   The section narrows into another segment of artery with diameter  d2 = 0.0022 m . The height relative to the laboratory floor  does not change (y1 = y2) . The density of blood is 1.06x103 kg/m3.   NOTE:   The diagram below shows  dimensions and arrows qualitatively  and may not be exactly at scale.

(a) (2 points)  What is the circular cross-sectional area  A1 of the first section of artery?

(b) (2  points) What is the circular cross-sectional area  A2 of the second  section ?  

(c) (5  points) What is the speed v2  in the narrow section of artery?  

(d) (7 points)  What is the pressure difference P1 – P2 between the two sections?

(e) (2 points) Short answer in sentence form or math form; just clearly explain your work: It was mentioned in class  a drop in pressure could lead to the collapse of the narrow section of artery. Explain. What would be one major consequence of such a collapse?

 

 

 

 

 

 

 

 

 


3.  (30 points)  When a container is filled to the brim with liquid, what happens when the temperature rises? You are doing a controlled experiment on a strange,  liquid  metallic substance.

A glass flask has volume  1.0x10 -3 m3 at 0.0 0C  and is completely filled (to the brim) with a strange,  liquid metal  at this temperature. The volume thermal expansion coefficient of glass is βg = 1.7x10 -5 (oC
) -1. When the flask and metal are warmed to 57.0 oC ,   some of the liquid metal overflows and the metal’s volume  thermal expansion coefficient  is found to be  βm = 18x10 -5 (oC)-1.

What is the volume of fluid metal that  overflows ?  When done, you might want to convert your answer to cm3 to better see the spill.
 

 

 

 

 

 

 

 

 

 

 

 




 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4 . (30  points)  Calculating required heats.  You have  a large supply super-cooled ice at  -10.0  oC to do informal experiments in your college dorm room. Thus,  the  initial temperature for all parts of  the problem below is  -10.0 oC .

You will also need the following information: Specific heat of ice Ci =  0.480 cal/(oC );  heat of fusion of water L
f = 79.9 cal/g, and specific  heat of water Cw = 1.00 cal/(oC ). 


(a) (20  points)   How much heat is required to convert 12.0 g of  ice  at
-10.0 oC to pure water at 55.0 oC? 

(b) (10  points)  How much heat is required to convert 12.0 g of  ice  at
-10.0 oC to a mixture of water and ice  0oC assuming the mixture is 50 % water? In other words, half  the 12 g piece of ice is melted. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


5.  (40 POINTS)   Below is a PV diagram showing a cyclic process for
0.0040 moles of an ideal monatomic gas. The direction of the cycle is shown by the arrows on the curve. The temperature does NOT change along segment ca – the process is isothermal from point c to point a.
The other 2 sections of curve are  graphically vertical and horizontal .

(a) (14  points) What volume does the gas occupy at point a?
(b) (14  points) What is the temperature at points  a, b and c?

For parts (c), (d) and (e) below, indicate whether the heat Q has gone into or out of the gas by referring to the sign, positive or negative, of your answer.

(c) (2 points)  How much heat went into or out of the gas during segment ab?

(d) (2 points)  How much heat went into or out of the gas during segment bc?

(e)  (2 points)  How much heat went into or out of the gas during segment ca?

For parts (f) , (g) and (h) below, indicate whether the change in internal energy ΔE int   is positive or negative by referring to the sign of your answer.

(f)  (2 points)  Find the change in internal energy during segment ab.

(g) (2 points)  Find the change in internal energy during segment bc.

(h) (2 points)  Find the change in internal energy during segment ca.

 

6. (30 POINTS)  An ideal gas undergoes a reversible expansion at
25.0 
oC.  During the expansion, the gas does 1825 J of work moving the piston upward as indicated in schematic below.  

(a) (24 points)  What is the change in entropy ΔS of the gas?

(b) (6   points)   Suppose the volume of the gas is doubled during the expansion. What is the number of moles n of the gas?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7.  EXTRA CREDIT (14 points) A uniform horizontal  beam has a mass of 13.0 kg . As you see below, the beam makes an angle of 45 degrees with a vertical pole.  The beam’s  right end is connected to a horizontal,  light (essentially mass-less ) cable.   The beam’s left end is hinged at pivot A on the rigid,  fixed  pole. The left end of the cable is also attached to the pole.  See figure.  Show all work.

 (a)  (6 points)   What is the tension T in the cable?
 (b)  (2 points)   What is the horizontal component  of  force FH exerted by pivot A on the beam?
 (c)  (2 points) What is the vertical component of force Fv exerted by pivot A on the beam ?
 (d)  (4 points)  Assuming the  beam length is 1.0 m, suppose a vandal severs the cable such that the tension becomes zero. Consider the moment just after the cable is cut and the beam is in a horizontal position.  At that instant, what is the magnitude of the torque (about pivot A)  exerted by the gravitational force?  What is the magnitude of the beam’s  angular acceleration about  point A at this instant?