The coefficients of static and kinetic friction between the 85-kg block and the
ID: 1859214 • Letter: T
Question
The coefficients of static and kinetic friction between the 85-kg block and the inclined plane are 0.31 and 0.25 respectively. Determine (a) the friction force F acting on the block when P is applied with a magnitude of 213 N to the block at rest, (b) the force P required to initiate motion up the incline from rest, and (c) the friction force F acting on the block if P = 560 N. The friction force F is positive if it acts up the incline and negative if it acts down the incline.
Please answer all parts of the question: (a), (b), and (c).
Thanks!
Explanation / Answer
a) normal force = 85gcos 16 - 213sin 21 = 724.399
max. static fricition force available = 224.44
downward horiziotal force = 85 g sin16 - 213cos 21 =30.753 which is less than 224.44
=> friciton force acting = 30.753 (upward)
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b) pcos(21) = 0.31( 85gcos 16 - psin 21) +85 g sin16
=> p = 287.921
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c) normal force = 85gcos 16 - 560sin 21 =600.0449
max. static fricition force available = 186
upward horiziotal force = 85 g sin16 - 560cos 21 =293.2 which is greater than 186
=>kinetic friciton force acting = 150.011