Which two of the following forces must always reduce the total mechanical energy of an object when present in a motion situation in which an object is sliding across a surface? ▪︎Spring
▪︎Applied
▪︎Tension
▪︎Gravity
▪︎Friction
▪︎Air Resistance
▪︎Normal​

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

there are no contact forces mentioned on the list of choices that you've provided.

not too sure thinking all accelerations are pointed down