I do agree with the previous posts saying that it's overlapping with fire bolt, and that there may be too many bolt spells already.
But, I really like this idea of a Gravity targeting spell; throwing a gravity-infused apple at the opponent for the kill sounds wonderful.
To make it different from fire bolt and yet have Gravity thematics included, how about we make Newton's Apple a "momentumed bolt spell"?
It would not be reflected by shields, and can hit immaterial creatures. I dunno if that will be overpowered, but a damage reduction to 2 damage per 10

would be nice if it's momentumed.
With the ability to hit immaterial creatures, I believe it will be a much better counter than damaging shields against quintessence.