The 6 foot long fishing pole AB is securely anchored in the

The 6 foot long fishing pole (AB) is securely anchored in the sand at point A. Once a fish takes the bait the tension in line BC becomes 6 lbs, represented in Cartesian form as {2.970i - 0.8350j - 5.146k} lb. Determine the moment about point A caused by the tension in the fishing line. Determine the moment about the AD axis caused by the tension in the fishing line. Each propeller of the twin-propeller ship develops a full speed thrust F = 300 kN. In maneuvering the ship one propeller is turning full speed ahead and the other is turning full speed in reverse What thrust P must each tug boat exert on the ship to counteract the effect of the ship\'s propellers.

Solution

The magnitude of the moment cause by a couple is equal the magnitude of the force multiplied by the distance separating the forces.

The thrusters apply a moment of (300 kN) (12 m) = 3600 kNm in the CW direction.

The tug boats are separated by 70 m to to apply the same magnitude moment they each need to apply a force of

P = 3600 kNm/70 m = 51.4 kN.