Mathematical and Physical Journal
for High Schools
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# Problem P. 4011. (October 2007)

P. 4011. Below the fixed end of the insulating horizontal thread, at a distance equal to the length of the thread there is a fixed charge, which has the same charge as the charge of the small body of mass m at the end of the thread as shown in the figure. The body is released and when it is at the lowest position the angle between the thread and the horizontal is 30o.

a) Find the mass of the moving body.

b) Find the tension at the lowest position.

c) By what factor is the acceleration of the body at the lowest position is greater than the initial acceleration?

(5 pont)

Deadline expired on November 12, 2007.

### Statistics:

 91 students sent a solution. 5 points: Almási 270 Gábor András, Balogh Gábor, Bartha 002 Zsolt, Blázsik Zoltán, Csányi Gergely, Csató Bertalan, Csengeri Béla, Cseppentő Lajos, Deli Gábor, Egyed Zsombor, Farkas Márton, Ferenczy László, Fonyó Dávid, Földes Tamás, Gaál Alexisz Tamás, Harsányi Szabolcs, Hartstein Máté, Hlatky Dávid, Iván Dávid, Király Anna, Kovács 888 Gábor, Krämer Zsolt, Kunsági-Máté Éva, Kupcsik Réka, Lászlóffy András, Lénárt Tamás, Lovas Lia Izabella, Lovász Krisztina, Marák Károly, Patartics Bálint, Pázmán Koppány, Piller Éva, Rárósi Dávid, Schlarb Krisztián, Somogyi József, Szabó 895 Dávid, Szikszay László, Szolnoki Lénárd, Tolnai Gábor, Tolner Ferenc, Tóth 123 László, Túri Attila, Velicsányi Péter, Vida György. 4 points: 17 students. 3 points: 8 students. 2 points: 7 students. 1 point: 5 students. 0 point: 8 students. Unfair, not evaluated: 2 solutionss.

Problems in Physics of KöMaL, October 2007