PHYS 158 Chapter 26.2-26.3 : Direct-Current Circuits & Electrical Measuring Instruments
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Calculus Based Physics | Physics For Scientists And Engineers withModern Physics (7th)by Serway, Jewett | 46 | 55AP | 6/10/2010 at 11:55:00 AM |
Question Details: Ans. given below isnotadequate. problem 55 ch 46 page 1390 asks for "the upper limit thattheobservation sets on the mass of a neutrino". Obs. was a supernova 170 000 ly away. 8 neutrinos in 6s, (energies betw. 8 MeV and 40 MeV) and 11 n's in 13 s ( 10 MeV n. needs 10 s more than photontotravel this distance) The expert solution does not give this ans. It only converts light years to seconds! The book gives the ans. as " 19 eV/(c squared)" Please explain this ans. Brian. |
Response Details:
19eV is energy in electron volts. 1 electron volt is1.6e-19Joules, so for very small energies it is more convenient touse theelectron volt rather than Joules.
From Einstein's equation e=mc*c, the solution you gave hasjustrearranged this to m=e/c*c
Was this what you needed clarification on?
My Response Details:
That is true but does this give the ans. 19 eV/c*c ?
m = e/c*c
m= 1.6 e -19/c*c but this is not = 19??
Sorry this is wrong. I have confused e for energy with eforelectronic charge.
Energy was 10 MeV,so m = 10 e^6/c*c.
This is still not = 19/c*c.
Please show how to get 19/c*c.
Brian.
Elisha Graves Otis invented the elevator brake in the mid- , making it possible to build tall skyscrapers with fast elevators. Todayās skyscrapers are a large fraction of a mile tall; for example. Taipei in Taiwan has stories and is ( miles) tall. The top speed of the elevator in the Taipei tower is roughly three times greater than the ascent rate of a commercial jet airplane. The position and time data in the table are based on such an elevator.
a. Working in SI units, make a position-versus-time graph for the elevator.
b. Describe the motion of the elevator in words.
c. Find the highest speed of the elevator. When is the elevator going at this speed?
d. What sort of considerations would the engineers need to make to ensure the comfort of the passengers?
Ā Position (stories) |
Ā Time (s) |
Ā Ā 0.0 | Ā 0 |
Ā Ā 0.3 | Ā 1 |
Ā Ā 1.1 | Ā 2 |
Ā Ā 2.5 | Ā 3 |
Ā Ā 4.4 | Ā 4 |
Ā Ā 6.8 | Ā 5 |
Ā Ā 9.8 | Ā 6 |
Ā 13.1 | Ā 7 |
Ā 16.4 | Ā 8 |
Ā 19.6 | Ā 9 |
Ā 22.9 | Ā 10 |
Ā 26.2 | Ā 11 |
Ā 29.5 | Ā 12 |
Ā 32.7 | Ā 13 |
Ā 36.0 | Ā 14 |
Ā 39.3 | Ā 15 |
Ā 42.5 | Ā 16 |
Ā 45.8 | Ā 17 |
Ā 49.1 | Ā 18 |
Ā 52.4 | Ā 19 |
Ā 55.6 | Ā 20 |
Ā 58.9 | Ā 21 |
Ā 62.2 | Ā 22 |
Ā 65.5 | Ā 23 |
Ā 68.7 | Ā 24 |
Ā 72.0 | Ā 25 |
Ā 75.3 | Ā 26 |
Ā 78.5 | Ā 27 |
Ā 81.6 | Ā 28 |
Ā 84.2 | Ā 29 |
Ā 86.5 | Ā 30 |
Ā 88.2 | Ā 31 |
Ā 89.6 | Ā 32 |
Ā 90.0 | Ā 33 |
Ā 90.0 | Ā 34 |
Ā 90.0 | Ā 35 |
Ā 90.0 | Ā 36 |
Ā