# Newton's Second law: Pushing the box

1. Feb 27, 2017

### aatari

1. The problem statement, all variables and given/known data

How much force is needed to push a 20 kg box across a floor at a constant speed of 0.5 m/s [forward] against a frictional resistance of 4 N?

2. Relevant equations
Fnet = m.a

3. The attempt at a solution
Since the velocity is constant, the acceleration will be 0. If that is correct the net force is going to be 0, which doesnt make any sense.

2. Feb 27, 2017

### Staff: Mentor

Why's that? Did you draw the Free Body Diagram?

3. Feb 27, 2017

### cnh1995

The "net" force is zero. You are asked to find the force that needs to be "applied" to the box.

4. Feb 27, 2017

### aatari

Is there a formula that I can use to find the "applied force"?

5. Feb 27, 2017

### Staff: Mentor

That's the purpose of this exercise: You're meant to find that formula by analyzing the problem using the given information.

As already mentioned, you need to draw the FBD to see how the forces combine.

6. Feb 27, 2017

### aatari

Is it going to be 4N because the forces have to be balanced?

7. Feb 27, 2017

Yes.