SOLUTION: A force of 100N acting horizontally to the right is to be combined with another force P acting upward to the right at an angle of 15 degrees with the vertical. If the resultant for

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Question 1182677: A force of 100N acting horizontally to the right is to be combined with another force P acting upward to the right at an angle of 15 degrees with the vertical. If the resultant force of these two forces is 122.83N, solve force P.​

-> Is it possible to use phytagorean theorem? I'm having a hard time understanding the problem. Please help..

Found 3 solutions by robertb, ikleyn, Edwin McCravy:
Answer by robertb(5830)   (Show Source): You can put this solution on YOUR website!
UPDATE: I have edited the solution to correct the fact that cos(105) is a negative quantity, based on what solution other tutors have given.

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Use the cosine law, which says that,
where is the angle between vectors and , and vector is the one opposite to .
Let , , and , the magnitude of the resultant force.

===>
<===> after simplifying.
===>
Therefore the magnitude of force P is around 50N.

Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
.
A force of 100 N acting horizontally to the right is to be combined with another force P acting upward to the right
at an angle of 15 degrees with the vertical. If the resultant force of these two forces is 122.83N, solve force P.​
~~~~~~~~~~~~~~~~


Use the parallelogram rule of adding vectors and use the cosine law,  which says that

        ,

where    is the angle between vectors    and  ,

and vector    is the sum of vectors     and  .


In our case,   ,  ,  and  ,  the magnitude of the resultant force.

===>   

===>      after simplifying.

===>   


Therefore, the magnitude of force P is around 50 newtons.             ANSWER

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Solved.



Answer by Edwin McCravy(20055)   (Show Source): You can put this solution on YOUR website!
Since it makes a 15o angle with the vertical, it makes a 75o angle with the
horizontal.





Yes, you can use the Pythagorean theorem.  I made a mistake somewhere, but
don't have time to find it and correct it. Maybe you can find the mistake.

      horizontal   |   vertical 
      components   |  components
---------------------------------
   |P|cos(75o) N   ||P|sin(75o) N
        100 N      |      0 N
---------------------------------
|P|(cos(75o)+100 N |  |P|sin(75o) N
               ______________________________________________________________ 
|Resultant| = √(sum of horizontal components)2 +(sum of vertical components)2



Square both sides









Subtract 10000 from both sides.







Since 









Use the quadratic formula:









We use the + since the - gives a negative value.









That's the magnitude of the force P.

The angle it makes with the x-axis is found by











Edwin

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