What is velocity ? and the formula of it?

Velocity is the measurement rate of a certain object as it moves towards other position over time. Therefore, it uses both the factors of speed and time in order to calculate its actual measurement. Velocity is calculated through the use of distance divided by speed; usually meters divided by seconds.

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

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray