If you use Move Object to throw things at people, it'll deal "incidental" damage, even if you don't have Ranks in the Damage Effect. Incidental Damage is the level of damage a normal person could do with their fists. This applies for every scenario in which you're in a conflict with others (in your personal and cooperative stories, feel free to be a bit more epic than your Effects would allow. Rule of Cool) and you do something that would cause damage, but don't have the Damage Effect. Such as driving a car into someone.
Yes, this means a car driving at 100 miles an hour could deal less damage than a knife. You can rationalize this as the target avoiding a direct hit, or some other circumstance arising that keeps them from taking a "realistic" blow.