two tug boats are towing a large boat, of mass 22500 kg, back to shore. tug boat 1 is pulling with forcce of 5500 N at an angle of 35 degree north of the forward motion and tug boat 2 is pulling with force of 4970.8 N at an angle 40 south of the forward motion. if the large boat is being pulled with constatnt velocity, and there is a resistive force to the motion, then what size is the resistive force?

Question

kainui · Answer

Draw a picture, and take a guess and I'll help you figure it out. =)

anonymous · Answer

You must find the force component that is doing the work.
For each tug boat, you must multiply the force by the cosine of the angle. Next, sum the two force components. You'll get total force that is doing the pulling. 
To find the resistive force, you'll need to know what is the friction coefficient between the large boat hull and the water, and multiply by the working force. That will give you the resistive force, or friction to the movement.
Vectorially, the friction force is linear to the movement but in opposite direction.

mrnood · Answer

You do not need all the Dheart says.
First resolve and sum the forces as he says
However - since the boat has constant velocity you know that there is no resultant force.
Therefore you can conclude that the resistive force is equal to the combined resolved forward acting forces.

mrnood · Answer

I should add - equal - but opposite. 
i.e. the resistive force has the same magnitude as the combined resolved forward forces, but acts in the opposite direction.