A helicopter is moving past some clouds at a velocity of 5 km/hr north relative to the clouds. The clouds are moving past the ground at a velocity of 3.5 km/hr north. How fast is the helicopter going past the ground?

their crystal patterns have been disrupted by stress

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

blue light is scattered in different directions by the tiny molecules of air. blue is scattered more than other colours because it has a shorter distance to travel which results in smaller waves. this is why we see a blue sky most of the time.