Mathematical and Physical Journal
for High Schools
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Problem P. 3976. (April 2007)

P. 3976. A disc of radius R is moved with a constant u velocity on an air-cushioned table. Another small disc collides with it elastically with a speed of v0=0.3 m/s, the velocities of the discs are parallel. The distance d shown in the figure is equal to R/2, friction between the discs is negligible.

a) For which u will the small disc move perpendicularly to its original motion after the collision?

b) What will be the speed of the small disc in this case?

(5 pont)

Deadline expired on May 11, 2007.


45 students sent a solution.
5 points:Balogh Máté, Bartha Zsolt, Csató Bertalan, Danka Miklós András, Dudás János, Egyed Lenke, Egyed Zsombor, Farkas Ádám László, Fonyó Dávid, Földes Imre, Hartstein Máté, Horváth Bence, Kupcsik Réka, Nagy 224 Csaba, Pásztor Ádám Viktor, Sándor Bulcsú, Szabó 895 Dávid, Szerző 147 Péter, Szilágyi Zsombor, Szűcs Gergely, Tűri Balázs.
4 points:Blázsik Zoltán, Englert Dávid, Pásztor Árpád, Tóth 123 László.
3 points:10 students.
2 points:3 students.
1 point:2 students.
0 point:1 student.
Unfair, not evaluated:4 solutions.

Problems in Physics of KöMaL, April 2007