Orbital Mechanics

Is there someone here who can do a short lesson on orbital mechanics please.

I understand faster launch speed = higher orbit = slower orbital speed and
the reverse.

I am having trouble with object 1 is x miles from object 2.
Object 3 is x miles from object 2. Same distance.

If object 1 adds 10 units of delta V in can get to object 2 in 24 hrs.

object 3 can only add .5 units of delta v. It can not get to object ever.

Thanks