# Magnitude of Force within incline?

by anglum
Tags: force, incline, magnitude
 P: 275 learningphysics the answer to part 1 was 36.356N so that is the hypotenuse in the triangle we have drawn so we can square that and subtract the dotted line^2 from the picture on page 2 in this thread and then solve for the Fn????
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P: 4,124
 Quote by johnsonandrew Me? No I get 20.3 or 20.4
20.33 in other words Fsin(34) is the perpendicular component of F... there are 3 forces perpendicular to the plane... the normal force, mgcos(34) and 20.3...

Normal force - mgcos(34) - 20.3 = 0

solve for normal force
 P: 275 Normal force then equals 24.4307N???
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P: 4,124
 Quote by anglum Normal force then equals 24.4307N???
no. how did you get that?
 P: 88 24.4 N?
 P: 275 Fn -53.9cos(34) -20.3 = 0 Fn = 53.9cos(34) + 20.3 Fn = 44.685 + 20.3 Fn = 64.9851N
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P: 4,124
 Quote by anglum Fn -53.9cos(34) -20.3 = 0 Fn = 53.9cos(34) + 20.3 Fn = 44.685 + 20.3 Fn = 64.9851N
yes. that's correct.
 P: 88 Fn- 54cos(34) - 20.3 = 0 Fn - 44.7 - 20.3= 0 <<---- Fn= 24.4 Edit: Nevermind I know what I did...
 P: 275 ok that is the correct answer so our problem was we werent calculating all 3 perpendicular forces... we were just finding one of them and using that as Fn.... however its all 3 of them equal to 0
 P: 88 I'm so confused... I'm gonna go read over all that again haha..
HW Helper
P: 4,124
 Quote by anglum ok that is the correct answer so our problem was we werent calculating all 3 perpendicular forces... we were just finding one of them and using that as Fn.... however its all 3 of them equal to 0
Yes, it is important to go with the basic equations, and get the results from there... don't take shortcuts...

the most important step is $$\Sigma{Fy} = 0$$, where y is perpendicular to the plane... plug in your forces into the left side... Fn - mgcos(34) - Fsin(34) = 0...
 P: 88 Ohhh
 P: 88 So Fn - Fg parallel - Fg perpendicular = 0 ?
 P: 275 thanks to all who have helped me .... tonite i finished earlier than usual... i got the other 9 problems sumwhat easily... thanks again
 P: 88 Thanks for posting it I learned something too. Thanks learningphysics..

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