• Support PF! Buy your school textbooks, materials and every day products Here!

Blocks on an Incline

  • Thread starter lollikey
  • Start date
  • #26
435
13
think about it, if the normal force = mgcos(theta) how can Fgx = mgcos(theta)?
 
  • #27
33
0
i thought the fg would break up into fg in and fg out and the fg in would match up fn. Im looking at a past problem we've done but we solved for acceleration
 
  • #28
435
13
ok so think about it like a triangle, the force collinear to the plane is Fgx, and the force orthogonal is Fgy, and Fn = Fgy.
 
  • #29
33
0
okay so fgy = 9.8mcos(theta) and fgx = 9.8msintheta)
 
  • #30
435
13
correct, ok so now that you know that, sum up all the forces in the x direction again.
 
  • #31
33
0
the forces in the x direction are fgx and fst

9.8msin(theta) + (9.8m)cos(theta) * .7
 
  • #32
435
13
fgx and fst are opposing forces, when you say "sum up the forces" you don't add the magnitudes. You have to set one direction to be positive and the other negative, so when they oppose forces one is negatively acting on the object and the other is positively acting on the object.
 
  • #33
33
0
this is sooo confusing!!! thank you soooooo much for helping me !!!!

so would it be 9.8msin(theta) - (9.8m)cos(theta) * .7
 
  • #34
435
13
yes it would be, now that you know what the sum of forces is recall what they are equal to from post 19-20.
 
  • #35
33
0
9.8msin(theta) - (9.8m)cos(theta) * .7 = 0

9.8msin(theta) = (9.8m)cos(theta) * .7

9.8msin(theta) /(9.8m)cos(theta)= .7

sin(theta)/cos(theta) =.7

tan(theta) = .7
 
  • #36
435
13
yes sir, and now you have the answer. ;)
 
  • #37
33
0
thank you sooo much!!!!!!!!!!!!!!!!!! you are the best ever!!!!!!
 
  • #38
435
13
No problem.
 

Related Threads for: Blocks on an Incline

  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
1
Views
12K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
10
Views
2K
  • Last Post
Replies
1
Views
1K
  • Last Post
Replies
3
Views
489
  • Last Post
Replies
2
Views
5K
  • Last Post
Replies
4
Views
3K
Top