Newton's Second Law: Solving for Acceleration and Velocity | Homework Help

[lauraosborn]

Homework Statement

http://postimage.org/image/810vdcuvf/

Homework Equations

F=ma

The Attempt at a Solution

for part a) i put mdv/dt = -F(brake) - kv

but is lost for what to put in for part b), help?

 

[Doc Al]

What is v at t = 0?

 

[lauraosborn]

What is v at t = 0?

for part b) am i right if i say that

-the speed is 15 when t=0
-the speed is decreasing

 

[Doc Al]

for part b) am i right if i say that

-the speed is 15 when t=0
-the speed is decreasing

The first is what I would call the initial condition.

 

[lauraosborn]

c) 1200 dv/dt = -(3600 + kv)
1/(3600+kv) dv = -1/1200 dt

so do i integrate the above equation to find k?

 

[Doc Al]

You're not finding k (I assume that k is given in your model of air resistance), but v(t).