How to ignore x and z in magnitude

[FoxiRocket2009 (Red_Spy)]

I need to calculate the change along the y axis, that is, if a part falls or rises, then the condition will be fulfilled. But for some reason, when I try to calculate it in the traditional way ((char.HumanoidRootPart.Velocity.Magnitude*Vector3.new(0, 1, 0)).Magnitude) is considered as if moving along the x and z axes, although I ignore them.

[0ffxInventor (Inventor)]

local velocity_y = char.HumanoidRootPart.Velocity.Y

[FoxiRocket2009 (Red_Spy)]

@0ffxInventor

Y

Thank you!!!