Question

3) Static friction Feel for yourself: Hold a book on your outstretched, perfectly horizontal hand. Quickly starting to move the book horizontally (speeding up) by moving your hand forward (that is, away from you) a) Which direction is your skin pulled by the book? Forward / backward (circle one) (hint: if you can't tell, you can exaggerate the effect by trying to move the book forward slowly while holding it back with your other hand) b) Which direction is the book being pulled by your skin? Forward / backward (circle one) c) Draw a free body diagram for the book. d) If you move your hand with TOO much acceleration under the book, it will slip out from underneath it. Imagine that you make careful experimental measurements using a book of mass m and determine that the maximum acceleration you can achieve without causing your hand to slip against the book is a. Determine an expression for the coefficient of static friction Hs between your hand and the book. Your answer may include one or more of the following: m, a, and the acceleration of free fall, g. e) Now suppose you accelerate the book forward at a slower rate so that it does not slip. Is the following statement true? "The magnitude of the static friction force between the book and your hand is equal to usmg" True / False (circle one) Explain your answer to this true/false question.

Answer 1

SeUTEON hand is mnoved foeward, due to mteiba, he book uiu bryto Lemain m is mibal state. hat meams t hamd moves foriond the book mibially is at rest on the zalm (tard).When the book wrlu move back, ward diretim (a the sken wiu oppore the mmoh'on op b0ok, the book ucle PulL skin m backwerd moh'on the book wru be pullkd by the skin m fowerd direchon (02 Skin wiit pull book m for ward direchlon book and hamd ( palm skin j h e bocy oliagram Ahow m gure there (c) ,Motionob book motiom >hand R (ol) Fma re marsthe book s m so the upwerd oirected rection d the thand en the book R= mg, amd he backwerd thand frichiemal for by skin on the book ii Us R = Usm ficaional forca C uhen hamd move with toomueh aneeleiation the guchonal the book is backwerd duechon) fora on F us m b mite mass' the hgnd ma = p ar usm) mla 7 usmg n no a F= ma $2 slip condition anreler ation we can ahievewithout chus the maxi mum uppeny obtha book a= (e gn part (e) we have calulated > a ug ohen hand moved the rictm0 moved ouy vebast th fozce thamd en the book,w wosk fos coard olirectien do Componcet it Th eictina fora on Ehe boook wu be te= yR=m oheu, us Coefficient stahc bictn Statement is true - T