Mathematical and Physical Journal
for High Schools
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Problem P. 4457. (September 2012)

P. 4457. A one end of a thread of length \ell is tied to a small iron ball, whilst the other end is fixed at a height of \ell above a tabletop. The ball is displaced such that the thread is horizontal and is kept at this position by an electromagnet. At a height of \ell above the tabletop another small iron ball, similar to the one at the end of the thread, is also kept by an electromagnet. The two electromagnets release the balls at the same moment. The two balls begin to move at the same instant.

Which one reaches the tabletop first?

(4 pont)

Deadline expired on October 10, 2012.

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

Megoldásvázlat. A szabadon eső test ér le hamarabb, hiszen az ingatest függőleges irányú gyorsulása a fonálerő miatt mindvégig g-nél kisebb.


238 students sent a solution.
4 points:92 students.
3 points:52 students.
2 points:51 students.
1 point:33 students.
0 point:10 students.

Problems in Physics of KöMaL, September 2012