Is a starting voltage the opposite of a stopping voltage?

[joe]

I was asked about this peculiar question from the 2014 HSC exam which is at
http://newt.phys.unsw.edu.au/jw/temporary/Q26.png

Note the polarity of the battery.
How (and where) do you think the KE of the electrons was measured?
How much of the experimental graph is extrapolation?

I'm told that the marking will take the difficulties of this question into account.
Joe

[a.s.h.]

I also found the wording of the question strange, since "maximum kinetic energy" usually refers to that when the electron has been emitted.

It took me a while to realise that they meant including the kinetic energy gained due to the battery's voltage.

[joe]

It took me a while to realise that they meant including the kinetic energy gained due to the battery's voltage.

I suppose it must be that, but it's not obvious to me how one would measure that.

And if that's what it means, then most of the line drawn is an extrapolation, and not a summary of experimental results. So it's a strange question.

Joe