Tangential force acting on a skier has been set to zero?

[influx]

Can anyone explain why sum of Ft has been set to be = 0? The slope is smooth so no frictional forces act but by setting it to 0 they are neglecting the component of the weight along the slope? Having said that, this is a curved slope and not a straight one so does the component of the weight along the direction of motion vary continuously (since theta varies?)

 

[CWatters]

If it's a parabola what is the slope at point A ?

 

[influx]

If it's a parabola what is the slope at point A ?

It's 0?

 

[CWatters]

So what is the "component of weight along the slope" at point A?