If the light completed the 71.0-km round trip in the time it took the mirror to complete one-eighth of a revolution, what is the speed of light?

An electron with a charge of -1.6 × 10^-19 coulombs experiences a field of 1.4 × 10^5 newtons/coulomb. what is the magnitude of the electric force on this electron due to this field? a. 1.6 × 10^-3 newtons b. 1.4 × 10^24 newtons c. 2.2 × 10^-14 newtons d. 7.4 × 10^-13 newtons e. 4.5 × 10^14 newtons