Physics 1407                                                    Test No. 3                                       Fall 1999

 

This is an old test  which you can use to practice for test #3.   Some questions have been dropped from the original because they will not be covered in the official version of test3.    This test does not cover all the material covered which test 3 will include.  Do not rely entirely on this test to practice.

 

I.                   TRUE – FALSE

 

1.      The pressures at the bottoms of the two open

      containers shown are the same, assuming

      the liquids are the same.

 

 

2.      Two objects, A and B, weigh the same even though the density of A is less than the density of B.  When submerged in water, object A will weigh less than object B.

 

 

3.      As ice floats in water, about 10% of the ice floats above the surface of the water.  If we float some ice in a glass of water we should find that the water level will not change as the ice melts.

 

4.      A piece of wood of mass M floats on the surface of water with two-thirds of its volume submerged.  The additional force needed to completely immerse the wood is Mg/3.

 

5.      A block of wood and a 1-kg mass of lead are placed in a bowl that is filled to the brim with water.  The 1-kg mass is lifted from the water by a thin wire, and as this is done, the level of the water drops a bit.  The lead mass is now placed on the block of wood, which remains afloat while supporting the mass.  As the lead is placed on the wood and floated, some water spills over the edge of the bowl.

 

6.      The speed of a particle undergoing SHM is a maximum when the force exerted on the particle is a maximum.

 

 

7.      A block of mass M is connected to a spring hanging from an overhead support and is        lowered slowly to equilibrium, stretching the spring 20 cm in the process.  The block is then pulled down, stretching the spring an additional 10 cm, and then released.  The amplitude of the ensuing oscillations will be 20 cm.

 

8.   Referring to the figure at the right, let P denote the gage pressure

       of the trapped air column.  One concludes that P = 12 cmHg.

 

 

9.    A uniform board of mass 20 kg and length 9.0 m is placed on a

       fulcrum 6.0 m from one end, and with a 10-kg weight suspended

       from the other end.  When the board is released, it will be balanced

      on the fulcrum and will not fall.

 

 

 

II.                MULTIPLE CHOICE

 

1.      A uniform, horizontal beam of length 6 m and weight 120 N is attached at one end to a wall     by a pin connection (so that it may rotate).  The opposite end is supported by a cable attached to the wall above the pin.  The cable makes an angle of 60° with the horizontal.  What is the tension in the cable needed to maintain the beam in equilibrium?

 

(a)     35 N               (b)  69 N            (c)  60 N

(d)  120 N        (e)  139 N

 

2.      A block of wood has density 0.50 gm/cm3 and mass 1500 gm.  It floats in a container of oil (the oil’s density is 0.75 gm/cm3).  What volume of oil does the wood displace?

 

(a)    3000 cm3                        (b)  2000 cm3                        (c)1500 cm3

(d)   1000 cm3                        (e)  2500 cm3

 

 

3.      A simple harmonic oscillator has a total energy E.  When the displacement is two thirds the amplitude, the kinetic energy is

 

(a)  1/3 E          (b)  2/3 E         (c)  2/9 E                   (d)  4/9 E     (e)  5/9 E

 

 

 

 

4.      An object of volume V has a mass density r, which is greater than the density of oil, r0 .  It is completely submerged in oil and supported by a rope,

as shown.  The tension in the rope is:

 

(a)  (r0 -r)Vg             (b)  (r0 + r) Vg          (c)  (r - r0) Vg            

 

(d)  rVg            (e)  r0Vg  

 

5.      A window for viewing fish in the wall of a dam is rectangular and measures 0.80 m x 1.2 m.  Its center is 12 meters below the surface.  What is the total force on the window?

 

(a)  176,400 N        (b)  113,000 N        (c)  120,400 N      (d)  141,200 N        (e)  11,500 N

 

 

6.      If a mass M is attached to a vertical spring and lowered slowly to equilibrium, the spring stretches an amount x.  If instead the mass is attached to the spring and dropped, find the maximum energy stored in the spring at the turning point where v = 0.

 

(a)  Mgx           (b)  Mg/x            (c)  x/Mg          (d)  2Mgx         (e)  Mgx/2

 

 

7.      A venturi tube may be used as the inlet to an automobile carburetor.  If the inlet pipe of 2 cm diameter narrows to 1 cm diameter, what is the pressure drop in the constricted section for airflow of 3 m/s in the 2 cm section?  (Assume air density is 1.25 kg/m3). 

 

(a)  70 Pa         (b)  85 Pa        (c)  100 Pa             (d)  115 Pa

 

8.      The length of a simple pendulum with a period on Earth of one second is most nearly

(a) 0.12 m        (b)  0.25 m             (c)  0.50 m             (d)  0.75 m

 

 

9.      A pendulum of length 50 cm oscillates with an angular frequency of 3 s-1 and an amplitude of 0.18 radians.  The speed of the pendulum as it passes through equilibrium is

 

(a)  0.27 m/s (b)  0.030 m/s         (c)  0.54 m/s (d)  0.060 m/s          (e)  27/p m/s

 

10.  A mass-spring system is set into oscillations with an amplitude A and angular frequency w.  How long does it take for the mass to move from  x = 0 to  x = A/2 (in units of 1/w)?

 

(a)  p             (b)  p/2         (c)  p/3         (d)  p/4         (e)  p/6