SOLUTION: hello there. can you please help me w/ this vectors hw question? it's from my "vectors as forces" lesson. A mass of 20 kg is suspended from a ceiling by two lengths of rope tha

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Question 1201559: hello there. can you please help me w/ this vectors hw question? it's from my "vectors as forces" lesson.
A mass of 20 kg is suspended from a ceiling by two lengths of rope that make
angles of 30° and 45° with the ceiling. Determine the tension in each of the ropes.
i tried to do it below...
30 degrees = F1
45 degrees = F2
20 x 9.8m/s^2 = 196 so 20 kg is 196N
break triangle in half;
triangle: 120 degrrees in middle, 45 on f2 side, 30 on f1 side
f1/sin45 = f2/sin30 = 196N/sin120
i'm not sure what i'm doing from here
thank you.

Answer by ikleyn(52786)   (Show Source): You can put this solution on YOUR website!
.

Let T1 be the tension of the rope 30°;  T2 be the tension of the rope 45°.


T1 and T2 are the magnitudes of the forces; their dimensions are newtons.


Force F1 has horizontal component T1*cos(30°) = .

Force F2 has horizontal component T2*cos(45°) =  in opposite direction.


Equilibrium condition in horizontal direction gives you this equation

    } = ,   or

     = .        (1)


Force F1 has vertical component T1*sin(30°) = .

Force F2 has vertical component T2*sin(45°) = .


Equilibrium condition in vertical direction gives you this equation

     + } = 20*g,   or

     +  = 40g.     (2)


Thus you have a system of two equations (1) and (2),  and now your task is to solve it.


For it, replace in equation (2) the term  }  by , based on equation (1).

You will get then

    T1 +  = 40g,   or

     = 40g,

    T1 = .


From equation (1), you get then

    T2 =  = .


At this point, the problem is just solved.


If you want to get the numerical values for magnitudes / (tensions)  T1  and  T2,  use your calculator.

Solved.



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