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(university of kansas)
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posted by  Arowana on 7/3/2009 12:34:08 PM  |  status: Live  |  Earned Karma: 46

need your help on problem 8.5 from chapter 8???

Course Textbook Chapter Problem Needs by
Classical Mechanics Vector Mechanics for Engineers: Statics (8th) by Beer, Johnston, Eisenberg 8 5P N/A
Question Details:
knowing that θ=25 degree, determine the range of values of P for which equilibrium is maintained?
Aro
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Oracle
Karma Points: 23,802
(University of North Florida)
posted by VSL on 7/3/2009 5:12:46 PM  |  status: Live
Clarification Details:
Did you meant to say that angle alpha is 25 degrees because I do not see a "theta" anywhere in your diagram?
"In physics, you don't have to go around making trouble for yourself - nature does it for you" - Frank Wilczek

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Guru
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posted by rooya(MNK) on 7/4/2009 8:31:07 AM  |  status: Live
Asker's Rating: Lifesaver   
Response Details:
 

Hi

Mass of the block and μ not provided in the problem

Value of p when the block is about to move up the plane

 Forces Normal to plane
N + Psin25 = mgcos20

N = (mgcos20-Psin25)

F = μ(mgcos20-Psin25)

Forces  along the plane

Pcos25 = mgsin20 + F

Pcos25 = mgsin20 + μ(mgcos20-Psin25)

Pcos25 + Psin25 = mg(sin20 + μcos20)

Pmax= [mg(sin20 + μcos20)]/[cos25 + sin25]
Value of p when the block is about to move down the plane


Forces Normal to plane

N + Psin25 = mgcos20

N = (mgcos20-Psin25)

F = μ(mgcos20-Psin25)

Forces  along the plane

Pcos25 +F = mgsin20

Pcos25 + μ(mgcos20-Psin25) = mgsin20

P(cos25 - μ sin25) = mg(sin20 - μcos20)

Pmin= [mg(sin20 - μcos20)]/[cos25 - sin25]

Substituting the values of W and μ  in the equations  
Range

Pmin <= P => Pmax
Novice
Karma Points: 46
(university of kansas)
posted by Arowana on 7/5/2009 1:48:40 PM  |  status: Live
Asker's Rating: N/A-Posted by Person Asking Question   
Response Details:

yes, theta is = 25 degree, and the static friction is 0.30 and the kinetic friction is 0.25 and the mass of the block is 10kg?  Thank you for helping...
Aro
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