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help please!!!

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Scholar
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Respect (93%):
Date Posted: 7/19/2008 2:31:29 PM  Status: Live
help please!!!
Course Textbook Chapter Problem
Classical Mechanics Vector Mechanics for Engineers: Dynamics (8th) by Johnston, Beer, Clausen 11 139P
Question Details:
Can anyone solve this problem please?? I dont understand it! please i need help!!!
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Answers:

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Sage
Karma Points: 4,554
Date Posted: 7/20/2008 1:35:26 AM  Status: Live
Asker's Rating: Lifesaver   
Response:
The initial speed is:
Vo = 72 km/hr = 20 m/s
And the tangential acceleration is
at = -1.25 m/s2
A)
So the total acceleration at t = 0 will be:
an = Vo2/ρ = (202) / 350 = 1.14286 m/s2
so
a = √(1.252) + (1.142862) = 1.69 m/s2
B)
And the total acceleration at t = 4 s
v = Vo + at*t = 20 + (-1.25)(4) = 15 m/s
an = 152/350 = .6426 m/s2
a = √1.252 + .64262 = 1.41 m/s2
Engineering ain't easy...



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