# Homework Help: Finding Drag w/ acceleration & Boyant force

1. Nov 3, 2008

### swede5670

1. The problem statement, all variables and given/known data
A speed boat is accelerating at 5 m/s/s. If the Boyant force (the force the prevents the boat from sinking) is 3140 N and the thrust that the motor exerts on the boat is 1876 N, what is the drag on the boat (drag in a fluid is a like friction on land).

2. Relevant equations
Fnet = ma

3. The attempt at a solution
We just started getting 2 part equations and I'm a little confused on what I have to solve for first. Would someone help me figure out what to solve for first?
I was thinking that since the boyant force is 3140N going up then gravity must be pulling 3,140N down right? So then the acceleration downwards is 9.81 m/s/s, so 3,140N = X * 9.81 then divide 3,140 by 9.81 and you get 320.081549kg. Does this help at all?
Fnet = ma
Fnet = (320kg * 5m/s/s)
If that is correct, what do I use for Fnet

2. Nov 3, 2008

### PhanthomJay

Yes looks good so far. The boat is accelerating in the x direction. The net force is the algebraic sum of the forces acting on the boat in the x direction. What are those forces? (one is given, the other is unknown; you need to solve for it).

3. Nov 3, 2008

### swede5670

1876 N - Ff = (320kg * 5m/s/s)

1876N/(320kg * 5m/s/s) = Ff

1.1725 is the force of friction? I'm pretty sure thats not right, what am I missing?

4. Nov 3, 2008