The science that uses principles of physics to understand the human machine is called

Biomechanics

Explanation:

Biomechanics is a branch of biophysics that uses principles of physics to study and understand movement in organisms using the laws of mechanics. One of the applications of Biomechanics is its usage in sport and exercise activities. Biomechanics is used to study body movement of athletes during sport or exercise activities to improve performance of athletes and make the activities better and safer.  

a straight line sloped

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