Quiz No 2 Solution:

Force BA is 100 N in magnitude. Find the magnitude and the components of the projection of this force into the line OB.

F_PROJECTION = (F_BA . u_OB) u_OB

F_BA = (100) [ (4-(-2)i + 8j -4k ] / (36+64+16)^1/2

= 55.71i + 74.28j – 37.14k

U_OB = ( -2i +4k) / (4+16)^1/2 = - 0.447i +0.894k

Then F_PROJECTION = (55.71i + 74.28j – 37.14k) . (- 0.447i +0.894k) [- 0.447i +0.894k]

= 25.97i – 51.95k