Is my teacher wrong? Problem dealing with forces.

  • #1

Homework Statement


Problem is in the picture


Homework Equations


The teacher told us the
Fnetx = 20N - Fx (Fx is 0)
Fnety = Fy - 50N (Fy = +25N)


The Attempt at a Solution


My answer was 32N. But my teacher said the answer was C. which was 77.5N. He got it because Fnety = 75N for him. But that to me doesn't make sense since the Fy and 50N are pointing in opposite directions, won't Fnety be = -25N?
 

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  • #2
Oh nvm i think i got it. I think he meant to put that:
25N = Fy - 50 huh? Darn and to think i could prove a teacher wrong ;"D
 
  • #3
Redbelly98
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Welcome to PF.
Oh nvm i think i got it. I think he meant to put that:
25N = Fy - 50 huh? Darn and to think i could prove a teacher wrong ;"D
Glad it worked out finally. The key here was to think carefully about which sign (+ or -) goes with each force -- including Fnety, which we know is + because the object accelerates in the +y direction.
The teacher told us the
Fnetx = 20N - Fx (Fx is 0)
Fnety = Fy - 50N (Fy = +25N)
It pays to be careful -- those forces in parentheses should read (Fnetx is 0) and (Fnety = +25N)
 

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