Force required to remove a stopper from a flask

[rasen58]

A flask is closed tightly with a rubber stopper 3.00 cm in diameter. All the air in the flask is then removed. How much force is necessary to remove the stopper from the evacuated flask? (1 atm = 1.013 x 10^5 N/m^2)

 

I have no idea how to do this problem. I think I'm supposed to use Bernoulli's equation, but I'm not sure how exactly to use it.

 

I also tried using P = F/A

So F = P*A = 1 x 10^5 x pi x (0.03)^2 = 283

But the answer is 71.6 N.

Edited March 2, 2015 by rasen58

[studiot]

 

But the answer is 71.6 N.

 

 

 

Well it would be.

 

Look very carefully at your calculation for the area of the stopper.

 

[rasen58]

Oh wow, I used the diameter instead of the radius. Thanks.