140 The Laws of Motion*P5.48Since the board is in equilibrium, Fx∑=0 and we see that the normalforces must be the same on both sides of the board. Also, if theminimum normal forces (compression forces) are being applied, theboard is on the verge of slipping and the friction force on each side isffnss==afmaxμ.The board is also in equilibrium in the vertical direction, soFfFyg∑=−=20, or fFg=2.The minimum compression force needed is thennfFsgs=()=μμ295 572 0..N20.663N.fnF= 95.5 NfngFIG. P5.48*P5.49(a)nFfnF+°−°=∴=−−sincos..,157525067 97 0 25924 67 0 094NmaxafµFor equilibrium:
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