Mathematical and Physical Journal
for High Schools
Issued by the MATFUND Foundation
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Problem P. 3994. (September 2007)

P. 3994. A 60 kg boy notices a nice fruit on a tree. Even with stretched arms he cannot reach it, he is a 0.5 m below the fruit. The boy crouches down - his centre of mass descends 0.4 m - and then he leaps up. Thus he just reaches the fruit. Assume that he exerts a constant force on the ground while he touches it.

a) What is this force at least?

b) What is the average power of the boy?

(4 pont)

Deadline expired on October 11, 2007.


282 students sent a solution.
4 points:113 students.
3 points:10 students.
2 points:61 students.
1 point:55 students.
0 point:38 students.
Unfair, not evaluated:5 solutions.

Problems in Physics of KöMaL, September 2007