Mathematical and Physical Journal
for High Schools
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Problem P. 4208. (December 2009)

P. 4208. Three marbles of mass 4m, m and 3m can slide without friction along a horizontal rod. (There are holes in the balls.) At a certain moment the middle marble is given an initial speed of v0=5 m/s towards the right. After the totally elastic collisions determine the

a) velocities of the marbles;

b) the ratio of the kinetic energies of the marbles.

(4 pont)

Deadline expired on January 11, 2010.

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

Megoldás. \(\displaystyle a)\) A bal oldali test balra halad 1 m/s, a középső jobbra 1,5 m/s sebességgel, a jobb oldali jobbra 2,5 m/s sebességgel.

\(\displaystyle b)\) A mozgási energiák aránya: \(\displaystyle E_{4m}:E_{m}:E_{3m}= 14:9:75\).


156 students sent a solution.
4 points:122 students.
3 points:8 students.
2 points:7 students.
1 point:8 students.
0 point:9 students.
Unfair, not evaluated:2 solutions.

Problems in Physics of KöMaL, December 2009