Finding Drag w/ acceleration & Boyant force

[swede5670]

Homework Statement

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).

Homework Equations

Fnet = ma

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

 

[PhanthomJay]

Homework Statement

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).

Homework Equations

Fnet = ma

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

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).

 

[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 that's not right, what am I missing?

 

[PhanthomJay]

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

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

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

Your algebra!
1876-Ff = 320(5)
Ff = 1876 - (320)5

 

[swede5670]

Haha thanks a lot, that was a dumb mistake.
I appreciate the help!