Pressure of Chair Legs: Find F/A for 72 kg Person

[eagles12]

Homework Statement

A 72 kg person sits on a 4.0 kg chair. Each leg of the chair makes contact with the floor in a circle that is 1.1 cm in diameter. Find the pressure exerted on the floor by each leg of the chair, assuming the weight is equally distributed.

Homework Equations

P=F/A
A=∏r^2

The Attempt at a Solution

To find the force, I added the mass of the person and the mass of the chair and got m=76kg. Then i multiplied that by g=9.81 and got F=745.56.
To find the area, I converted 1.1 cm into meters, .011, and found the area A=9.5*10^-5
then i divided F/A and got P=7845260 but this is incorrect.

 

[HallsofIvy]

Homework Statement

A 72 kg person sits on a 4.0 kg chair. Each leg of the chair makes contact with the floor in a circle that is 1.1 cm in diameter. Find the pressure exerted on the floor by each leg of the chair, assuming the weight is equally distributed.

Homework Equations

P=F/A
A=∏r^2

The Attempt at a Solution

To find the force, I added the mass of the person and the mass of the chair and got m=76kg. Then i multiplied that by g=9.81 and got F=745.56.

Okay, that's good.

To find the area, I converted 1.1 cm into meters, .011, and found the area A=9.5*10^-5
then i divided F/A and got P=7845260 but this is incorrect.

Did you recall that the chair has four legs? Oh, and be sure to include units of measurement.