What is essential to accurately represent all physical quantities?
Correct Answer: \( \boxed{\mathrm{C}} \)
Every physical quantity must be stated with both a numerical magnitude and an appropriate unit.
Scientific notation is useful but not always required, and some quantities are not expressed using SI units.
Therefore, the correct answer is (C).
What is a reasonable estimate of the weight of an adult human?
Correct Answer: \( \boxed{\mathrm{B}} \)
The weight of an adult human is typically about \(70\,\mathrm{kg}\).
Using \(W=mg\), \(W\approx70\times9.8\approx686\,\mathrm{N}\), which is approximately \(7\times10^{2}\,\mathrm{N}\).
Therefore, the correct answer is (B).
Which physical quantity could have units of \( \mathrm{Ns^{2}\,m^{-1}} \)?
Correct Answer: \( \boxed{\mathrm{C}} \)
Since \( \mathrm{N=kg\,m\,s^{-2}} \),
\( \mathrm{Ns^{2}\,m^{-1}=kg\,m\,s^{-2}\times s^{2}\times m^{-1}=kg} \).
The derived unit is the SI unit of mass.
Therefore, the correct answer is (C).
