What statement is true about stable air?
1) its never associated with precipitation
2) it tends to rise
3) it is associated with severe storms
4) it tends to resist rising

Option (4) is the correct answer.

Explanation:

A stable air is defined as the one which tends to resist movement. On the other hand, an unstable air will easily rise from one place to another.

By nature, stable air masses are calm and free of any violent disturbances. These are most of the time noticed by their appearance of stratiform clouds or fog.

Thus, we can conclude that the statement it tends to resist rising is true about stable air.

the minimum amperage that the current in this wire would have to have so that its weight is completely supported by the magnetic force due to earth's field, assuming that no other forces except gravity act on it

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s