To find the barrel's speed, use a calculator to divide the distance traveled (100 m) by the time it took the barrel to float 100 m. The units are meters
per second (m/s).

The comparison of the number of atoms in a copper coin the size of a penny with the number of people on earth is made to illustrate which of the following? a. that atoms are indivisible b. that atoms are very small c. that atoms are very large d. that in a copper penny, there is one atom for every person on earth