Questions   
Sort: 
 #1
avatar+11912 
+3
Sep 15, 2014
 #3
avatar+118724 
+5
Sep 15, 2014
 #12
avatar+11912 
+3
Sep 15, 2014
 #1
avatar+33665 
+5

Let FAB be the force in cable AB and FBC be the force in cable BC.  Let θA be the angle between cable AB and the horizontal and θC be the angle between cable BC and the horizontal.

 

Horizontal force balance

FABcos(θA) = FBCcos(θC)          ...(1)

Vertical force balance

FABsin(θA) = mg + FBCsin(θC)  ...(2)

m = 2000kg; g = 9.81m/s2.

 

We also have that θA = tan-1(5.6/2.2) and θC = tan-1(2.4/5.6)

 

Replace FBC in (2) by using (1)

FABsin(θA) = mg + FABcos(θA)sin(θC)/cos(θC)

Rearrange to get FAB

FAB = mg/(sin(θA) - cos(θA)sin(θC)/cos(θC))

$${\mathtt{FAB}} = {\frac{{\mathtt{2\,000}}{\mathtt{\,\times\,}}{\mathtt{9.81}}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{5.6}}}{{\mathtt{2.2}}}}\right)}\right)}{\mathtt{\,-\,}}{\frac{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{5.6}}}{{\mathtt{2.2}}}}\right)}\right)}{\mathtt{\,\times\,}}\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{sin}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{2.4}}}{{\mathtt{5.6}}}}\right)}\right)}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{2.4}}}{{\mathtt{5.6}}}}\right)}\right)}}}\right)}} \Rightarrow {\mathtt{FAB}} = {\mathtt{25\,347.418\: \!086\: \!936\: \!201\: \!807\: \!8}}$$

FAB ≈ 25.347 kN

 

Substitute this back into (1) to get FBC

FBC = FABcos(θA)/cos(θC)

$${\mathtt{FBC}} = {\frac{{\mathtt{25\,347.418}}{\mathtt{\,\times\,}}\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{5.6}}}{{\mathtt{2.2}}}}\right)}\right)}}{\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{cos}}{\left(\underset{\,\,\,\,^{\textcolor[rgb]{0.66,0.66,0.66}{360^\circ}}}{{tan}}^{\!\!\mathtt{-1}}{\left({\frac{{\mathtt{2.4}}}{{\mathtt{5.6}}}}\right)}\right)}}} \Rightarrow {\mathtt{FBC}} = {\mathtt{10\,083.657\: \!337\: \!858\: \!801\: \!218\: \!7}}$$

FBC ≈ 10.083 kN

Sep 15, 2014

0 Online Users