[cc100]

a stress of 3.2MN m -2 is applied to a sample of material.
this requires a force of 80N.

use the following formula to calculate the area over which that force acts.

note MN m-2 is equal to N mm-2 so u dont need to do any unit conversions.

you will need to rearrange the formula

STRESS= FORCE/AREA.

[Sticks]

Area = Force / Stress

Area = 80N / 3.2 Nmm-2

Newton units cancel
1 over 1/a = a

so units of answer are in mm^2

Numerical answer is therefore

25mm^2

or in conventional units as we were taught.

2.5 x 10^-5 m^2

[cc100]

very good, very quick.

have you solved that one you left me before??

[Sticks]

I was waiting for your solution to that one