Solving Pressure & Force Homework Problem

[vrobins1]

Homework Statement

"A lid is put on a box that is 10 cm long, 16 cm wide, and 8.0 cm tall and the box is then evacuated until its inner pressure is 7.2e4 Pa."

How much force is required to lift the lid at sea level?

Homework Equations

I know that I have to use P=F/A
I changed my centimeters to meters also, although I'm not sure you have to.

The Attempt at a Solution

I used F = PA
F= (Atmospheric pressure - inner pressure)(lxw)
F=(100000 - 72000)(.10x.16)
F=(28000)(.016)
F=448 N

I tried this answer but got it wrong. Can someone please point me in the right direction? Thanks!

 

[vrobins1]

I figured it out! I just used a more accurate number for my atmospheric pressure instead of simply 10000.

 

[thomate1]

I would first check the units and make sure they are consistent. In this case, the units for pressure are in Pascals (Pa), while the units for area are in square meters (m^2). Therefore, the force calculated in the attempt at a solution is incorrect.

To solve this problem, we can use the formula F = P x A, where F is the force required, P is the pressure, and A is the area of the lid.

First, we need to convert the dimensions of the box from centimeters to meters. This can be done by dividing each dimension by 100.

10 cm = 0.1 m
16 cm = 0.16 m
8.0 cm = 0.08 m

Now, we can calculate the area of the lid by multiplying the length and width of the box:

A = (0.1 m) x (0.16 m) = 0.016 m^2

Next, we can plug in the given pressure value and the calculated area into the formula:

F = (7.2e4 Pa) x (0.016 m^2) = 1152 N

Therefore, the force required to lift the lid at sea level is 1152 Newtons.