This might be a very simple question. I read one previous post Can the kinetic energy be a function of the position vector?
I know that in Cartesian coordinates, the kinetic energy T=12mv2. And T is not an explicit function of position. So ∂T∂x=0, where we suppose x is a coordinate.
But I got confused by one example, we have a ball move vertically from the origin O, with a velocity of →V0.
then when the ball reach y1 in the positive y axis, we have mgy=12mv20−12mv21
so the velocity at y is v1=√12mv20−mgy
Does it means that velocity and kinetic energy both are explicit function of position y in this case? I know this is a special case, but the statement that ∂T∂x=0 in Cartesian coordinates seems to be quite general. So where have I missed so far? Thanks guys!
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