Mathematical and Physical Journal
for High Schools
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# Problem P. 4699. (January 2015)

P. 4699. Two thin sheets on the surface of a  slope of angle of elevation of $\displaystyle \alpha=30^\circ$ form a pair of rails. The distance between the sheets is $\displaystyle d=1.6$ cm. A ball of diameter of 2 cm is placed to the rails and it rolls down without slipping.

$\displaystyle a)$ Calculate the acceleration of the centre of the ball.

$\displaystyle b)$ If the coefficient of friction is $\displaystyle \mu$, at what angle of elevation will the ball slip on the rails?

(5 pont)

Deadline expired on February 10, 2015.

### Statistics:

 53 students sent a solution. 5 points: Asztalos Bogdán, Bekes Nándor, Bencsik Bálint, Blum Balázs, Csathó Botond, Fehér Balázs, Fülöp Erik, Holczer András, Iván Balázs, Kaposvári Péter, Kasza Bence, Kormányos Hanna Rebeka, Körmöczi Dávid, Lőrincz Zoltán, Öreg Botond, Varju Ákos. 4 points: Bugár 123 Dávid, Csenger Géza, Forrai Botond, Olosz Balázs, Szentivánszki Soma , Varga-Umbrich Eszter. 3 points: 12 students. 2 points: 6 students. 1 point: 9 students. 0 point: 4 students.

Problems in Physics of KöMaL, January 2015