How Much Force is Needed to Move a Wire with Soapy Solution?

[EmilyO89]

1.
Calculate the force needed to move the wire in the figure (Figure 1) if it holds a soapy solution (surface tension is 0.025 N/m) and the wire is 16.0 cm long.

Express your answer to two significant figures and include the appropriate units.

2.

γ(surface tension) = F (force) / l (length)

3. My attempt at a solution

γ=F/l so γl=F

γ: 0.025 N/m

l: 16cm or 0.16m

0.025 N/m * 0.16m = 0.004 N or 4.0 * 10^-3N

I know this must be ridiculously easy but I really can't figure out what I'm missing here. Do I need another equation to solve this problem? Am I messing up the units somehow?

 

[RonL]

1.
Calculate the force needed to move the wire in the figure (Figure 1) if it holds a soapy solution (surface tension is 0.025 N/m) and the wire is 16.0 cm long.

Express your answer to two significant figures and include the appropriate units.

2.

γ(surface tension) = F (force) / l (length)

3. My attempt at a solution

γ=F/l so γl=F

γ: 0.025 N/m

l: 16cm or 0.16m

0.025 N/m * 0.16m = 0.004 N or 4.0 * 10^-3N

I know this must be ridiculously easy but I really can't figure out what I'm missing here. Do I need another equation to solve this problem? Am I messing up the units somehow?

I can't help at this time, but someone will pretty soon:) I just have time to say welcome to PF and hope you stay around and get to know some people:D

 

[Chestermiller]

Look very carefully at the second part of the figure.

Chet

 

[EmilyO89]

Look very carefully at the second part of the figure.

Chet

Got it. Thank you!

I knew it must be something simple like that but I was getting hung up because I just could not visualize exactly what this thing is supposed to look like.

 

[HalfLostAndSearching]

Your approach is correct, but you are missing the units in your final answer. The units for surface tension (γ) are N/m, and the units for length (l) are m, so the units for force (F) should be N (newtons). Your final answer should be 0.004 N.