1.5 Estimates and Fermi Calculations
Attacking a question with no given data by assuming plausible sizes and rates, then combining them into a defensible estimate.
University Physics Volume 1, 1.5 Estimates and Fermi Calculations
6 exercises
1.5 Exercise 1
the reference says the mass of the atmosphere is 1019 kg. Assuming the density of the atmosphere is 1 kg/m3, estimate the height of Earth’s atmosphere. Do you think your answer is an underestimate or an overestimate? Explain why.
1.5 Exercise 3
Assuming the human body is primarily made of water, estimate the number of molecules in it. (Note that water has a molecular mass of 18 g/mol and there are roughly 1024 atoms in a mole.)
1.5 Exercise 5
Estimate the number of molecules that make up Earth, assuming an average molecular mass of 30 g/mol. (Note there are on the order of 1024 objects per mole.)
1.5 Exercise 7
Roughly how many solar systems would it take to tile the disk of the Milky Way?
1.5 Exercise 9
The average density of the Sun is on the order 103 kg/m3. (a) Estimate the diameter of the Sun. (b) Given that the Sun subtends at an angle of about half a degree in the sky, estimate its distance from Earth.
1.5 Exercise 11
A floating-point operation is a single arithmetic operation such as addition, subtraction, multiplication, or division. (a) Estimate the maximum number of floating-point operations a human being could possibly perform in a lifetime. (b) How long would it take a supercomputer to perform that many floating-point operations?
Adapted from University Physics Volume 1 © 2016 Rice University. Licensed under CC BY 4.0. Source: University Physics Volume 1. Imported at revision db44eb9.