A BALL IS TRHOWN UP STRAIGHT WITH A SPEED OF 10 M/S. WHEN THE VELOCITY WILL BE 0

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

snell's law

refractve index = sin incidence / sin refraction