Consider the following equations of motion.
v = v0 + at
îx = v0t + 1/2at^2
v2 = v02 + 2aîx

a. can the equations above be used in a situation where the acceleration varies with time?
b. can they be used when the acceleration is zero?

A) No, the equations presented above are the product of the derivation of position and velocity when the acceleration is constant.

The equations change to polynomial function of the second degree for the description of the acceleration when described as a function of time.

B) Yes, when the acceleration is zero it is concluded that the velocity is constant, therefore they could be used to describe the position as a function of the change in velocity.

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