Determine the magnitude and direction of the couple moment D

Determine the magnitude and direction of the couple moment.

Determine the magnitude and direction of the couple moment.

	M=2496 lb?ft CCW
	M=2496 lb?ft CW
	M=3120 lb?ft CW
	M=3900 lb?ft CW

Solution

vector in the direction of force B = ( 6i + 8j )

unit vector = ( 6i + 8j ) / 10 = 0.6i + 0.8j

force vector = magnitude *unit vetor = 120(0.6i + 0.8j)

r = (6i - 8j )

moment 1= r x F = (6i - 8j ) x 120(0.6i + 0.8j)

= 120 ( 0.8x 6k + 8 x0.6k)

vector in the direction of force A = (- 6i - 8j )

unit vector = ( - 6i - 8j ) / 10 = - 0.6i - 0.8j

force =120 ( - 0.6i - 0.8j )

r = (-8i + 8j)

moment 2 = r x F = 120 ( 8*0.8 k + 0.6*8 k)

total moment = 120 ( 4.8 + 4.8 + 6.4 + 4.8)k = 2496 lb ft CCW