6 Problems and exercises
Problems & Exercises
How many heartbeats are there in a lifetime?
Sample answer: [latex]2×{\text{10}}^{9}[/latex] heartbeats
A generation is about one-third of a lifetime. Approximately how many generations have passed since the year 0 AD?
How many times longer than the mean life of an extremely unstable atomic nucleus is the lifetime of a human? (Hint: The lifetime of an unstable atomic nucleus is on the order of [latex]{\text{10}}^{-\text{22}}\text{ s}[/latex].)
Sample answer: [latex]2×{\text{10}}^{\text{31}}[/latex] if an average human lifetime is taken to be about 70 years.
Calculate the approximate number of atoms in a bacterium. Assume that the average mass of an atom in the bacterium is ten times the mass of a hydrogen atom. (Hint: The mass of a hydrogen atom is on the order of [latex]{\text{10}}^{-\text{27}}\text{ kg}[/latex] and the mass of a bacterium is on the order of [latex]{\text{10}}^{-\text{15}}\text{ kg.}[/latex])
Approximately how many atoms thick is a cell membrane, assuming all atoms there average about twice the size of a hydrogen atom?
Sample answer: 50 atoms
(a) What fraction of Earth’s diameter is the greatest ocean depth? (b) The greatest mountain height?
(a) Calculate the number of cells in a hummingbird assuming the mass of an average cell is ten times the mass of a bacterium. (b) Making the same assumption, how many cells are there in a human?
Sample answers:
(a) [latex]{\text{10}}^{\text{12}}[/latex] cells/hummingbird
(b) [latex]{\text{10}}^{\text{16}}[/latex] cells/human
Assuming one nerve impulse must end before another can begin, what is the maximum firing rate of a nerve in impulses per second?
Glossary
- approximation
- an estimated value based on prior experience and reasoning
