Comic-book superheroes are sometimes able to punch holes through steel walls. (
ID: 1987881 • Letter: C
Question
Comic-book superheroes are sometimes able to punch holes through steel walls.(
a) If the ultimate shear strength of steel is taken to be 2.70 109 Pa, what force is required to punch through a steel plate 1.70 cm thick? Assume the superhero's fist has cross-sectional area of 8.00 101 cm2 and is approximately circular.
My professor told me that I got the problem wrong because I used the wrong area. He told me not to use the area of the fist, but i'm still getting it wrong.
Explanation / Answer
from the area of fist, find out the radius Then A = 2*pi*r*t where, t = thickness = 1.7 cm = 0.017 m then, tau = F/A => 270109 = F/A Substitute to get F