How fast will it be traveling after it goes 87 m ?

To solve this we can use one of the main four kinematic equations, preferably we want something that we can use directly without solving for other values.

So in this problem we know that:

Inital velocity or Vi = 0 (started from rest)

The acceleration of the object = 7.5

The distance the object travels Δx = 87m

So, our best equation here with what we have would be:

Vf² = Vi² + 2aΔx

Now we now that Vi is 0 so:

Vf² = 2aΔx

We need final velocity so lets take the square root of Vf to isolate it:

Vf = √2aΔx

Now we plug in

Vf = √2(7.5)(87)

Vf = 36.124 m/s or 36.1 m/s

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