Mathematical and Physical Journal
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Problem P. 4317. (February 2011)

P. 4317. A skewer of mass m=1 g is hanged with a short thread attached to a fixed point P. A long thread is attached to the bottom end of the skewer, and it is kept in equilibrium with a horizontal force. In this case the angle between the skewer and the vertical is \alpha. a) Find the angle between the short thread and the vertical. b) Find the tension in the short thread, if \alpha=45o.

(4 pont)

Deadline expired on March 10, 2011.

Sorry, the solution is available only in Hungarian. Google translation

Megoldás. \(\displaystyle a\)) A forgatónyomatékok egyenlősége miatt a pálcára ható három erő hatásvonalának egy ponton kell áthaladnia, amiből a kis fonal függőlegessel bezárt szögére a \(\displaystyle tg \varphi=\frac{tg\alpha}{2}\) összefüggést kapjuk.

\(\displaystyle b\)) A rövid fonálban ébredő erő nagysága \(\displaystyle F'=\frac{\sqrt{5}}{2}mg\approx 11\) mN.


105 students sent a solution.
4 points:69 students.
3 points:18 students.
2 points:9 students.
1 point:5 students.
0 point:1 student.
Unfair, not evaluated:3 solutions.

Problems in Physics of KöMaL, February 2011