[填空题]
A 75.0$-\mathrm{kg}$ person stands on a scale in an elevator. What does the scale read (in N and in kg ) when the elevator is
(a) at rest,
(b) ascending at a constant speed of 3.0 $\mathrm{~m} / \mathrm{s}$ ,
(c) falling at 3.0 $\mathrm{~m} / \mathrm{s}$ ,
(d) accelerating upward at 3.0 $\mathrm{~m} / \mathrm{s}^{2}$ ,
(e) accelerating downward at 3.0 $\mathrm{~m} / \mathrm{s}^{2}$ ?
