Finding force to push 11.2 kg box at constant velocity with friction

[moondawg]

Homework Statement

A stockroom worker pushes a box with mass 11.2 kg on a horizontal surface with a constant speed of 3.50m/s. The coefficient of kinetic friction between the box and the surface is .20. What horizontal force must the worker apply to maintain the motion?

Homework Equations

F=ma
F=$$\mu$$N

The Attempt at a Solution

First I drew my free body diagrams of course and found my Normal force to be 109.76N. Then i used this number and plugges it into F=ma(F=11.2x3.5) and got 39.2. Then using the 2nd equation above I found F=21.95. I was not sure if i was doing it correctly but then i added the 39.2+21.95= 61.152 as my F and answer. But I realized this cannot be right because i used 3.5 as my acceleration when it is just a constant velocity so I do not know how to even approach this question... PLEASE HELP!

 

[Dale]

You and tatiana really need to team up:
https://www.physicsforums.com/showthread.php?t=440097

So if the speed is constant then what is the acceleration? Remember the definition of acceleration and see if it applies here.

 

[jmb88korean]

If velocity is constant than all forces are equal. Force of friction will equal the applied force. Just do Force friction= normal fprce x coeddicient of kinetic friction. Since forces are equal they will be the same value.