Acceleration of object with friction: Homework help

[APphysicsSenior]

A 50 kg box rests on the floor. The coefficients of static and kinetic friction are 0.70 and 0.50, respectively.
a.) What is the minimum force required to start the box sliding from rest?
b.) After the box starts sliding, the person continues to maintain that force. What is the acceleration of the box?

Homework Equations

: μ=Ff/mg Fnet=ma[/B]3. I solved part A by using the force of static friction and my answer was 343 N, but I can't figure out part B. I figured since the net force on my force diagram was zero and the box is sliding at a constant velocity, that the acceleration would be zero, but that isn't correct. Any ideas?

 

[Doc Al]

I figured since the net force on my force diagram was zero

The net force is zero only before it begins sliding. Once it starts sliding, what happens to the friction force?