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 
. a) Find the angle between the short thread and the vertical. b) Find the tension in the short thread, if =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 \(\displaystyle F'=\frac{\sqrt{5}}{2}\textrm{~mg}\approx 11\) mN.
Statistics:
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 solutionss.
Problems in Physics of KöMaL, February 2011