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posted by  Nic - CE on 1/11/2008 7:10:20 PM  |  status: Closed  

Projection Force

Course Textbook Chapter Problem
Classical Mechanics Engineering Mechanics - Statics 11th by Hibbeler 2 119P
Question Details:
How did they get 31.1 N? (Step 4) I don't know if they are multiplying and how they are doing it. Thanks ahead of time for any advice you can give.
 
Projection Force,
Fab = F.λab
= (-35.3i - 41.2j - 58.8k) . ( -0.857i - 0.429j + 0.284k)
= 31.1 N
 
Fab = 31.1 N
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posted by Cacing on 1/12/2008 12:27:57 AM  |  status: Live
Asker's Rating: Lifesaver   
Nic - CE's comment:
"Thank you, appreciate it."
Response Details:
Question:
How did they get 31.1 N? (Step 4) I don't know if they are multiplying and how they are doing it. Thanks ahead of time for any advice you can give.
 
Projection Force,
Fab = F.λab
= (-35.3i - 41.2j - 58.8k) . ( -0.857i - 0.429j + 0.284k)
= {(-35.3*-0.857) + (-41.2*-0.429) + (-58.8*0.284)
= 30.2521 + 17.6748 - 16.6992
= 31.2277 ˜ 31.2 N
= 31.1 N
 
Fab = 31.1 N
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posted by aZraeL on 1/12/2008 10:49:19 AM  |  status: Live
Asker's Rating: Helpful   
Nic - CE's comment:
"Thank you, appreciate it."
Response Details:
Fab = F.λab
= (-35.3i - 41.2j - 58.8k) . ( -0.857i - 0.429j + 0.284k)
= 31.1 N

dot product: 

= (-35.3 * -0.857)
+ (-41.2 * -0.429)
+ (-58.8 * 0.284)

= (30.2521) + (17.6748) + (-16.6992)
= 31.2277 N
Fab = 31.1 N

The book converted the answers from English units to SI units, causing the small difference.
I hope this can help you. Thank you for rating!
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posted by Jetsadaporn on 7/24/2008 3:28:46 AM  |  status: Live
Asker's Rating: N/A   
Response Details:
How did they get vector rA ?I don't get like they get.How can you find it?
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