Final answer:
The best unit to measure the mass of 5 pennies is grams, as they would collectively weigh around 12.5 grams. In scale drawings, units such as mm or cm are used to represent actual measurements, and for force vectors, the drawing's scale can quantify the force represented.
Step-by-step explanation:
When considering the weight of 5 pennies, grams would be the most appropriate unit for measuring mass. Each penny has a mass close to 2.5 grams, so together, they would weigh around 12.5 grams. This is clearly more substantial than milligrams but less than a kilogram, making grams the right unit of measure for this scenario.
If the question is related to a scale drawing, each square may represent 10mm on the actual object being represented. When dealing with force vectors, a 5 cm length on a drawing could be representing a 50 N force if the scale is set such that 1 cm equals 10 N on the drawing.