Plot schematically the shear versus normal stress curve corresponding to a laboratory shear test and explain how it is disferent for a smooth fracture surface than that of a rough surface? what surface property would be estimated if the test is performed under a negligible normal stress?

Because if a good speech is delivered badly it can bore the audience, confuse them, or make them distrust the speakeri think they all come back to this one, except that last answer because that is false. if your audience starts making fun of you or gets distracted it is because they are either bored, confused or distrust you.