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

General College Physics (Phy 202) Test 4

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. **

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Name and Signature of Student _____________________________

Signed by Attendant, with Current Date and Time: ______________________

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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

What is the deBroglie wavelength of an electron moving at 7.2 * 10^6 m/s?

Problem Number 2

A certain hypothetical atom contains 77 protons and 110 neutrons in its nucleus and has an atomic mass of 186.2 atomic mass units, or amu (an amu is approximately 1.66 * 10^-27 kg). How many protons and how many neutrons will it end up with if it undergoes an alpha decay? How many if it undergoes a beta decay? How many if it undergoes a gamma decay?

Problem Number 3

How much energy will an electron in orbit about a hydrogen atom lose in a transition from orbit # 2 to orbit # 3, where orbits are counted from the closest outward? If this lost energy is carried away by a photon, what will be its wavelength?

Problem Number 4

A photon of 115.5458 nm electromagnetic radiation encounters an electron in the n = 2 orbital of a hydrogen atom, and causes it to 'jump' to the n = 3 orbital. What will be the wavelength of a photon which carries away any excess energy from the collision?

Problem Number 5

A spacecraft moving at constant velocity .89 * c relative to a nonaccelerating observer keeps time by reflecting a light pulse back and forth between two mirrors oriented at a right angle to the direction of motion. The mirrors are 100 meters apart (big spaceship) and are mounted within a sealed vertical vacuum tube (vertical being perpendicular to the direction of motion) so that the light pulse will travel at its vaccuum speed.

If we assume that the laws of physics are the same in the reference frame of the spaceship as in the frame of the observer, it follows that the speed of light in a vacuum will be identical in both reference frames.

Under this assumption:

How long does it take a pulse to travel from the lower mirror to the higher, as measured in the spaceship?
How long does it take the pulse to travel from the lower mirror to the higher as measured by the observer outside the spaceship?
If the pulse rate of an inhabitant of the spaceship is 74 beats/minute, as measured by that individual, then what pulse rate would be measured by the outside observer, assuming some accurate means of making the observation?

Problem Number 6

The intensity of light with a mean wavelength of 585 nm falling on a solar sail is 310 watts/m^2. The sail is oriented perpendicular to the direction of the incoming light, in order to intercept as much light as possible.

What is the total momentum of the photons falling on 82000 m^2 of the sail every second?
If the sail is a perfect mirror, reflecting the photons without any absorption or change in their momentum, then what average force is exerted on the sail?
How long would it take to accelerate a 2640 kg craft (mass includes that of the sail) from rest to velocity .1 c using such a sail?

Problem Number 7

Find the velocity an electron in a circular orbit would require at a distance of 2.544 Angstroms from a proton. Find the deBroglie wavelength of this electron. Determine the potential and kinetic energies of an orbit at this distance. Could this orbit exist? [ The mass of an electron is 9.11 * 10^-31 kg; the proton has a much greater mass; Planck's Constant is 6.62 * 10^-34 J s; k = 9 * 10^9 N m^2 / C^s ]

Problem Number 8

A hypothetical atom with negligible kinetic energy has a mass of 205 amu. It undergoes a beta decay. The remaining atom has atomic mass 204.5 amu. What is the kinetic energy and/or wavelength (whichever is more appropriate) of the emitted particle, assuming that the kinetic energy of the remaining atom is negligible? How much energy would be released by the decay of a mole of these atoms? Note that the mass of a helium nucleus is about 4.001 amu and the mass of an electron about .00055 amu, where an amu is approximately 1.66 * 10^-27 kg?