Mathematical and Physical Journal
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Problem P. 4332. (March 2011)

P. 4332. Two balls, made of soft copper alloy of specific heat capacity 400 J/(kg.K), collide head on. The initial speeds of the two balls, A and B, were the same and oppositely directed. After the collision ball A stops and ball B bounces back with the same speed as it had before the collision. Because of the collision the temperature of the balls increased with \frac{1}{3}~{}^\circC. At least what was the speed of the balls before the collision?

(4 pont)

Deadline expired on April 11, 2011.

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

Megoldás. A golyók ütközés előtti sebessége legalább \(\displaystyle v=20~\rm m/s\) volt.


126 students sent a solution.
4 points:94 students.
3 points:4 students.
2 points:7 students.
1 point:13 students.
0 point:7 students.
Unfair, not evaluated:1 solutions.

Problems in Physics of KöMaL, March 2011