A 3.0 kg rock is dropped from rest. What will its velocity be in 6.0 s if a 7.0 N force of air resistance acts on it?

14 m/s^2

Explanation:

final velocity

initial velocity

a= acceleration

t=time

Initial velocity is zero, since the rock was originally at rest and time is 6 seconds.

You are looking for the final velocity, but you need acceleration to find it. Remember that:

Where F is force, m is mass, and a is acceleration. You know force is 7.0 N and mass is 3.0 kg. Use these to find a.

So now...

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

i think the answer would be reserve.