If there is a potential difference V between the metal and the detector, what is the minimum energy Emin that an electron must have so that it will reach the detector

Emin= eV

Explanation:

This minimum amount of energy is the work function and so for an electron to reach the detector the energy must b more than work function and the stopping potential so

Emin=eV

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west