Test 2

Question 1

The buoyant force on an object fully or partially submerged in fluid must point

Answer 1

directly away from the center of the earth (regardless of object’s direction of velocity)

Question 2

The Hydrostatic Pressure Equation requires which of the following assumption(s)

Answer 2

• the fluid is acted on by a gravitational force
• the fluid is at rest (or negligible viscosity and moves at constant velocity)

Question 3

The continuity equation comes from the physical idea(s) that…

Answer 3

-there is no fluid gained or lost in a fluid with laminar flow, so mass flow rate is constant

Question 4

For an object obeying Hooke’s Law, the restoring force

Answer 4

• always points towards quilibrium
• has greater strength the greater the value of the spring constant
• gets stronger with large displacements from equilibrium

Question 5

What would increase wave speed in a mechanical wave?

Answer 5

decreasing density

Question 6

The wavenumber is

Answer 6

inversely proportional to wavelength of the wave

Question 7

What affects whether two waves have constructive interference at a location X?

Answer 7

• difference in distance traveled between the waves’ sources and the location X
• whether the waves’ sources are out of phase with one another

Question 8

One in-class demo showed a pipe which connected two wide segments of pipe with a narrower segment of pipe. Air moved through the pipe. Why did the balls levitate higher above the wide tubes?

Answer 8

the pressure in the tube is highest in the wide part

Question 9

an object was fully submerged in water while its top was attached to a spring scale. What equation would give the correct relationship for the force exerted on the object by the spring scale?

Answer 9

mobject(g)-pfluid(g)Vobject

Question 10

At your initial location, the intensity is 10W/m^2. You move to a location that has an intensity level that is 50dB smaller. What is the intensity at the new location

Answer 10

10^-4 W/m^2

Question 11

At your location, the intensity due to a 250Hz sound is 10 W/m^2. If a 30W source emits this sound, which travels in all directions, how far in meters are you from the source?

Answer 11

sqrt[30/(4pi10)]

Question 12

A horizontal mass-spring starts oscillating from a position on the negative side of equilibrium. Case (a) is started with an initial speed of 3cm/s in the negative direction. Case (b) is started with an initial speed of 5cm/s in the positive direction. Case (c) is released from rest. Rate the cases in order of largest to smallest.

Answer 12

b>a>c

Question 13

An ideal, horizontally-oriented mass-spring consists of a 1.5kg mass and a 15N/m spring. Consider the cases(a), (b), and (c) described in the previous problem. Rate the cases in order of largest to smallest.

Answer 13

a=b=c

Question 14

Consider a simple harmonic oscillator moving in the x-direction. At the time with the dot on velocity vs. time graph, the oscillator is…

Answer 14

At the maximum amplitude on negative side of equilibrium

Question 15

A vertical simple harmonic oscillator is below equilibrium and moving upward. At this time…

Answer 15

the spring force is directed upward and the oscillator is speeding up.

Question 16

In which case(s) would location X experience perfectly destructive interference of two waves from coherent sources(Assume no reflections)

Answer 16

• The sources are perfectly out of phase and the path difference is exactly one wavelength
  -The sources are perfectly in phase and the path difference is exactly one-half wavelength

Question 17

Two waves are shown on separate lines in the picture so the waves can be seen, but they meet at the same point P. Which of the following is/are true at the time shown and all future times?

Answer 17

• the waves are not coherent

Question 18

What equation relates to the speed of a wave(as it propagates forward through the medium) to other physical properties of the wave?

Answer 18

• v=(lambda)f
  -v= sqrt[T/mu]

Question 19

We have a transverse wave on a string that is created by an oscillating source. The wave obeys the position equation y = Asin(k1x-wt). if the oscillation of the source does not change in height or frequency, but the tension in the cord doubles, wat could show possible equations of the wave over all space and time?

Answer 19

y= A1sin(k2x-w1) with k2<k1

Question 20

A U-shaped tube containes two different liquids in equilibrium which do not mix. 10mL of liquid R(pR=0.95 g/L) and liquid B (pB=0.89 g/L) 25mL. If liquid B is NOT present on the right side, which is true about the fluid levels on the two sides.

Answer 20

the level where the fluid meets the atmosphere is higher on the left side.