PHYS 2021 Lecture 3: Estimates (Jan 18, 2019)

• School: Temple University
• Department: Physics
• Course: PHYS 2021
• Professor: Dr. Tsvetelin D. Tsankov

Document Summary

Read on being the right size [posted on class page] Estimations: great to use because we cannot always be precise. A book with about 600 pages is about of an inch thick. In m: 1 inch = 2. 54 cm, 100 cm = 1 m. Estimating the radius of the earth using the eiffel tower as a vantage point. Note: d2 = h2 +s2 (r+h)2 = r2 + d2. R = s2 = 60 x 103 x 60 x 103 = 6x106 = 6000m. Estimate the typical distance between water molecules . Distance between molecules (d) can be estimated: d ~ a. Mass of each h2o molecule: (18 g / mol)(1 mol / 6. 022 x 1023) a. = 3 x 10-23 / 106 molecule/m3 = 3x10-9 m2/molecule. = 3 x 10-23 g/molecule a = v1/3 x 301/3 x 10-30/3 ~ 3 x 10-10 m/molecule. Since a ~ d, d ~ 3 x 10-10 m apart.