Question 2
How is one newton (1 N) written in base units?
The right answer is the one marked above.
1 kg m s−2. The newton is defined as the force needed to give unit mass (1 kg) unit acceleration (1 m s−2).
F = m a = 1 kg × 1 m s−2 = 1 N
1 kg m s−1 is the unit of momentum — mass × velocity. Do not confuse the two; the only difference is the power of the second.
It is because the unit was chosen this way that the constant in F = ma comes to 1.