Why does Bohr's model contradict Heisenberg's uncertainty principle?

Explanation

Accordinng to Bohr's theory, negative charged particles (electrons) inside an atom revolve aroucleus in well-defined orbits having fixed radius. In order to balance the nuclear attractive force, electron must move with a definite velocity. however, according to uncertainty principle, it is impossible to determine simultaneously the exact position and the momentum (or velocity) of a microscopic particle like electron. thus, bohr's model contradicts heisenberg's uncertainty principle.