Find velocity of boat as function of the time

[ays]

Homework Statement

a motorboat of mass m moves along a lake with velocity Vi. at the moment t=0 the engine of the boat is shut down, assuming the resistance of water to be proportional to the velocity of the boat f= -rv , find the velocity of the boat as a function of time

Homework Equations

ƩF = ma
a = dv/dt

The Attempt at a Solution

ƩF = ma
- mg - rv = ma
dv/dt = (-mg - rv)/m
am not sure if i am going the right way or not

 

[TSny]

Hello.

Force and acceleration are vector quantities. You should work with components:

ΣF_x = ma_x

ΣF_y = ma_y

 

[Niladri Dan]

I think that you should not consider mg as it is in 90° angle with rv

 

[jbriggs444]

I think that you should not consider mg as it is in 90° angle with rv

And it is in equilibrium with buoyancy.