String tension

1. May 9, 2004

UrbanXrisis

Two strings are attached to a 5 kg mass. String one is at a 45 degree angle and the other is horizontal. What is the tension in string one?

2. May 9, 2004

arildno

From my reading of this, String one is the only one capable of counteracting the weight of the mass (since it alone has a vertical component).

The tension in string one (i.e magnitude of tensile force) should therefore be:
sqrt(2)*mg.

3. May 9, 2004

UrbanXrisis

where did the sqrt(2) come from?

your equation works but how did you get it?

4. May 9, 2004

arildno

Assume that string one goes along the line (-cos(45),sin(45)), wheras string two is along the horizontal (1,0) (The mass itself is position at the origin).

(Clearly, the only necessary requirement is that the tensile force in string one has a component in the positive vertical component, in order to balance the weight of the mass).

5. May 14, 2004

KnowledgeIsPower

T1 = 63.9N
T2 = 49N

I just resolved horizontally and vertically
T1sin45 = 5G
Simplification gives T1 = 63.9N

Calculating T2 is optional, but i got 49N.

6. May 14, 2004

KnowledgeIsPower

To be sure, is the above correct? I'm revising for my mathematics - mechanics exam and that seems to be similar to a few of the questions.

7. May 14, 2004

Chen

Yes that's correct KnowledgeIsPower.

ΣFx = 0 = T2 - T1cos 45o
ΣFy = 0 = T1sin 45o - mg

From the second equation you can find T1, and the first will give you T2.