Could you cast Levitate on yourself, float off of the ground, then use the Mage Hand cantrip and your action to push yourself 30' horizontally? Mage Hand can manipulate no more than 10 pounds, but Levitate appears to make the target weightless as, other than vertical movement, they can move horizontally by essentially vaulting off of a wall or crawling along a ceiling.
I suppose it's possible. Spending an action (or bonus action for a Rogue) to mage hand yourself in an open area doesn't seem too powerful. I'm not sure if I'd ever personally do it in a game, though.
It cannot manipulate more than 10 lbs - and levitate doesn't make you massless, but does make you weightless.
The key here is whether the weight or mass are important to the Mage Hand spell's limitations.
I would argue inertia wins purely for game balance purposes - but I would see the counter-arguement as valid too - it's very much a GM call with no right or wrong in the 'physics'.
The correct answer is "no" but you may be able to convince your DM anyway. 
Caliburn101. wrote:
As with any other stated action in the game, if the DM thinks it works, then it does. If it doesn't, then it doesn't. If the DM thinks the outcome is uncertain, he or she can call for an ability check.
Nothing in levitate's spell description indicates that the target is weightless. But while it says the target can move only by pushing or pulling against a fixed object or surface, this would seem to indicate the target is the one attempting to move. It says nothing about being moved. So I would say that if a caster levitated himself, he could use mage hand to move the caster no faster than half his speed (as if climbing). If the caster tried to use mage hand on a target he levitated unwillingly, perhaps that target could get a Constitution saving throw to resist being pushed or pulled.
The magic section is written in the vernacular, not with actual physics. There is a pound (force) and a pound (mass), but the rules never specify which unit the term means.
I'd rule that mage hand can't apply more than 10 lbs of force to an object, which is pretty slow, but technically possible. Then again, most of the magic is based on an Aristetelian model of physics (what it looks/feels like the spell should do, rather than what Newtonian/quantum physics dictates that it should do).
Now I'm wondering if one could blow away a levitating spellcaster with a Gust of Wind spell.
Ganymede425 wrote:
I would totally allow it. I see no reason why it would not work. I'm actually surprised this hasn't come up before.
I'd allow it but at a significantly reduced speed, otherwise your getting a cheap fly.
I like inventive use of spell combinations
Ganymede425 wrote:
To me it all boils down to whether one assumes that levitate makes the caster weightless/(nearly) frictionless, or whether it just provides a "force" that lifts the caster off the ground gently but otherwise behaves like a solid surface under the character.
If you use the first case, mage hand would be more likely to be able to provide opposing force for a "push off." In the second case, it wouldn't really work due to how weak mage hand is (it can't shove people who are standing on the ground.) I'm partial to the second case myself, but I could see others adopting the first and using it as a push, which I don't think is at all overpowered.