Physics II

Time and Date Stamps (logged): 17:12:20 06-10-2020 ｰｶ涓ｱ浤ｯｯｵ涓ｯ浤ｯｱｯ Physics II

University Physics (Phy 232, Phy 242) Test 2

Completely document your work and your reasoning.

You will be graded on your documentation, your reasoning, and the correctness of your conclusions.

** Write clearly in dark pencil or ink, on one side of the paper only. **

Test should be printed using Internet Explorer. If printed from different browser check to be sure test items have not been cut off. If items are cut off then print in Landscape Mode (choose File, Print, click on Properties and check the box next to Landscape, etc.).

Name and Signature of Student _____________________________

Signed by Attendant, with Current Date and Time: ______________________

If picture ID has been matched with student and name as given above, Attendant please sign here: _________

Instructions:

Test is to be taken without reference to text or outside notes.
Graphing Calculator is allowed, as is blank paper or testing center paper.
No time limit but test is to be taken in one sitting.
Please place completed test in Dave Smith's folder, OR mail to Dave Smith, Science and Engineering, Va. Highlands CC, Abingdon, Va., 24212-0828 OR email copy of document to dsmith@vhcc.edu, OR fax to 276-739-2590. Test must be returned by individual or agency supervising test. Test is not to be returned to student after it has been taken. Student may, if proctor deems it feasible, make and retain a copy of the test..

Directions for Student:

Completely document your work.
Numerical answers should be correct to 3 significant figures. You may round off given numerical information to a precision consistent with this standard.
Undocumented and unjustified answers may be counted wrong, and in the case of two-choice or limited-choice answers (e.g., true-false or yes-no) will be counted wrong. Undocumented and unjustified answers, if wrong, never get partial credit. So show your work and explain your reasoning.
Due to a scanner malfunction and other errors some test items may be hard to read, incomplete or even illegible. If this is judged by the instructor to be the case you will not be penalized for these items, but if you complete them and if they help your grade they will be counted. Therefore it is to your advantage to attempt to complete them, if necessary sensibly filling in any questionable parts.
Please write on one side of paper only, and staple test pages together.

Test Problems:

. . . . . . . . . . . . . . . .

Constants

Constants:

k = 9*10^9 N m^2 / C^2	qE = 1.6 * 10^-19 C	h = 6.63 * 10^-34 J s
energy of n=1 orbital in hydrogen atom: -13.6 eV	k ' = 9 * 10^-7 T m / amp	atomic mass unit: 1.66 * 10^-27 kg
electron mass: 9.11 * 10^-31 kg	speed of light: 3 * 10^8 m/s	Avogadro's Number: 6.023 * 10^-23 particles/mole
Gas Constant: R = 8.31 J / (mole K)	proton mass: 1.6726 * 10^-27 kg	neutron mass: 1.6749 * 10^-27 kg

Problem Number 1

If a traveling wave has wavelength 2 meters and propagation velocity 145 m/s, what is the frequency of the wave? What is the period of a cycle of the wave?

Problem Number 2

The fundamental harmonic in a uniform string of length 6 meters, held under tension 40 Newtons, is 36 Hz. What is the mass of the string?

Problem Number 3

A string defines the x axis, with the origin at the left end of the string. The string has tension 11 Newtons and mass per unit length is 9 grams / meter. The left-hand end of the string is displaced perpendicular to the string in a cyclical manner in order to create a traveling wave in the string. At clock time t the position of the left-hand end of a long string is y = .91 cm * sin ( ( 8 `pi rad/s) t ).

What equation describes the displacement a point 11 meters down the string as a function of clock time?
If the position of the left-hand side is x = 0, what is the equation for the displacement as a function of clock time at arbitrary position x?
University Physics: Show that your equation satisfies the wave equation.

What is the equation for the shape of the string at clock time t = .062 sec?

Problem Number 4

Show that the function y(x,t) = .79 sin( 310 t - .78 x ) satisfies the wave equation, and give the equation of motion for the point at x = 3.31.

Problem Number 5

A string defines the x axis, with the origin at the left end of the string. The string has tension 37 Newtons and mass per unit length is 18 grams / meter. The left-hand end of the string is displaced perpendicular to the string in a cyclical manner in order to create a traveling wave in the string. At clock time t the position of the left-hand end of a long string is y = .59 cm * sin ( ( 5 `pi rad/s) t ). Explain where the energy is in this wave, and find the energy per unit length of the wave.

Problem Number 6

Traveling waves are set up in a pair of long strings by a single harmonic oscillator. The strings have identical mass densities of 5.7 grams / meter. Both strings terminate at a short bungee cord attached to a wall. The harmonic oscillator is attached to the other ends of the strings in such a way that one string is 8.1 meters longer than the other. If the oscillator has frequency 106 Hz:

Give at least two string tensions which will produce the maximum motion of the bungee cord.

Give at least two string tensions which will produce the minimum motion of the bungee cord.

Problem Number 7

If hearing threshold intensity is 10^-12 watts/m^2, then what is the intensity of a sound which measures 48 decibels?

Problem Number 8

A person 1.86 meters high stands 3 meters from a converging lens. A real inverted image of size .77 meters forms on the other side of the lens.

How far from the lens does the image form?
What is the focal length of the lens?
Sketch a diagram explaining how the image forms.

Problem Number 9

A string of length 7 meters is fixed at both ends. It oscillates in its second harmonic with a frequency of 183 Hz and amplitude .59 cm. What is the equation of motion of the point on the string which lies at 1.4 meters from the left end? What is the maximum velocity of this point?