Niels bohr's theory was based on evidence from a beam of particles that scattered after hitting thin gold foil. evidence that an atom will actually emit colors when heated. the experimental results of other scientists. the effect of holding a magnet next to a beam of electrons.

Evidence that an atom will actually emit colors when heated.

Explanation: Bohr's postulates include:

a) Negatively charged electrons orbit a positively charged nucleus in orbits with fixed energy levels.

b) The energy of the orbit keeps on increasing as it move far from the nucleus.

c)  An atom absorbs or emits radiation when an electron moves from one orbit to another.

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