Steel pulling through ice, find weight of object

[Ockonal]

Homework Statement

Steel object is pulling uniformly through the ice with applied force 2 Newtons. Find object's weight (P), if k of friction is 0.02

Homework Equations

F = 2 Newtons
k = 0.02
P - ?

F = m*a
P = m*g

The Attempt at a Solution

I drow all forces and made this:
ma = F_attraction + F_friction + N + F
X: ma = F - kN
Y: 0 = N - mg
N = mg;

ma = F - kmg
=>
ma = 2 - 0.02×m×9.8

But there is 'a' - acceleration. And in the exercise said: uniformly, so there shouldn't be an acceleration. But what to do if the second Newton's law is F = ma?

 

[jdc15]

And in the exercise said: uniformly, so there shouldn't be an acceleration. But what to do if the second Newton's law is F = ma?

That's right, there is no acceleration. According to Newton's second law, F=ma, if a = 0, then what happens to net force?

 

[Ockonal]

To tell the truth, I'm not sure.

 

[jdc15]

So we have F=ma, and a=0, we get F = 0. This means the two forces must cancel out.

 

[Ockonal]

But this way there shouldn't be any moving, should it?

 

[Ockonal]

Oh, if I understand you right:
0 = F - kN;
0 = N - mg;

N = mg;
0 = F - kmg
0 = 2 - 0.02×k×10
k = 10;
P = m×g;
P = 10×10 = 100 (Newtons)
And that is answer.
Thanks, but did I understand right, there there woudnlt' be moving?

 

[moondawg]

To find the weight of the object just remember to plug in all given variables into the equation F=$$\mu$$N. Force and $$\mu$$ are given so all you have to do is work with those 2 variables to find your normal force and thus find your weight (F=mg).

 

[jdc15]

Well, if you got the right answer, then it looks like you did the math right. But, there is still movement. Force doesn't directly cause there to be a velocity, it only causes acceleration. If there is no force, there is no chance in velocity, but there still can be movement.

 

[Ockonal]

Thanks all.