# Can't solve this physics problem?

Need help solving these hard physics problems...please help!

Question 1

Estimate the number of air molecules in a room of length 5.0 m, width 3.1 m, and height 2.6 m. Assume the temperature is 18°C.

Give your answer in scientific notation, as in the example for Avogadro's Number 6.02E23 with one number in front of the decimal point and two behind.

Question 2

Super Invar, an alloy of iron and nickel, is a strong material with a very low coefficient of thermal expansion [0.2x10-6/C°]. A 1.94-m-long-tabletop of this alloy is used for sensitive laser measurements where extremely high tolerances are required. How much will this alloy table expand along its length if the temperature increases 5.55°C?

Give your answer in microns where 1um = 10-6m.

### 2 Answers

- 1 decade agoBest Answer
Question number 2:

CTE states that for every degree C of temp change the dimension will change by 0.2x10-6 for your Invar alloy.

So what must we do?

simple, multiply 5.55 x 0.2 10-6 to get the delta change of the alloy.

then multiply this by the length of 1.94m to get how much the dimensional change has occured.

since we have been given different units, convert the 1.94 meters to microns before you do the multiplication so that the answer is in microns.

- daugaardLv 43 years ago
you're able to frequently contain parenthesis to make sparkling the function you mean: as written, the branch comes after the exponentiation. notwithstanding this feels like a Resistor-Capacitor RC time circuit, so i assume that the authentic difficulty is: 0.88 (seconds) = a million - e^(-8 / (R * one hundred thirty uF)). First, subtract a million from the two facets and multiply by ability of -a million: 0.12 = e^(-8 / (R * 130x10^-6)) Now take the ln of the two facets: ln 0.12 = -2.12 = -8 / (R * a million.30 x 10^-4) R * a million.30 x 10^-4 = -8 / -2.12 = 3.773 R = 3.773 / a million.30x10^-4 = 2.ninety x 10^4 ohms = 29.0 K?