I'm using Love2D and my own physics engine to create a 2D platformer. Y collision works fine, but X collision... well, it's a bit buggy. When I move off of a small platform I've created, I fall but it is a lot slower than what my gravity is set to. Here's my code for collision:

function world.collisionCheck(o)
    for k, v in pairs(world.objects) do
        if v ~= o then
            if v.Type == "Rectangle" and o.Type == "Rectangle" then
                if o.Position.Y + (o.Size.Y / 2) > v.Position.Y - (v.Size.Y / 2) then o.Velocity.Y = 0; o.onGround = true; end
                if not (o.Position.X + (o.Size.X / 2) > v.Position.X and o.Position.X - (o.Size.X / 2) < v.Position.X + (v.Size.X)) then o.onGround = false; end --right left
            end
        end
    end
end

As you can see, it's pretty bad. The code for the actual physics (gravity, movement, etc.) is a bit better:

function world.update(t)
    for k, v in pairs(world.objects) do
        if v.Static ~= true then
            v.Position.X = v.Position.X + v.Velocity.X
            if v.onGround == false then if v.Velocity.Y < world.Gravity then v.Velocity.Y = v.Velocity.Y + world.Gravity * t end end
            v.Position.X = v.Position.X + v.Velocity.X * world.Meter
            v.Position.Y = v.Position.Y + v.Velocity.Y * world.Meter
            v.Velocity.X = v.Velocity.X * world.Friction
            world.collisionCheck(v)
        end
    end
end

However, it could still use some work. Whenever I step off of a 150 pixel by 15 pixel platform, I fall a lot slower than 9.8 meters per second. My meters are set to two pixels, and I'm falling at about a meter per second, which is much slower than the expected ~20 pixels per second I get while still on the platform. Everything I've tried doesn't seem to fix it; there's no problem in the movement code, and nothing I change in the collision code seems to fix it. Is there some silly problem I've overlooked?