On May 11, 1998, at 1630 central daylight time, a Cessna 172N, N733HY, operated by Mid America Aviation, Inc., nosed over during a forced landing. The forced landing resulted from a loss of engine power during an initial takeoff climb from runway 17 (3,990' x 74') at the Hannibal Municipal Airport, Hannibal, Missouri. The student pilot received minor injuries. The airplane was substantially damaged. The 14 CFR Part 91 local flight was operating in visual meteorological conditions without a flight plan. The flight was originating at the time of the accident. The student pilot reported that everything was normal during the aircraft preflight and engine run-up. He reported the takeoff was normal until he was over the end of the runway at 200 to 300 feet above the ground at whoch time the engine lost power. He stated he applied carburetor heat and that "...seemed to help a little for 30-45 seconds." He returned the carburetor heat to "cold" and the engine rpm didn't change much. He stated the engine then lost all power and the propeller completely stopped. The pilot reported he turned to the right and make a forced landing in a plowed field. Post accident inspection of the airplane and engine by an Inspector from the St. Louis Federal Aviation Administration Flight Standards District Office failed to reveal any mechanical failure/malfunction which would have resulted in the loss of engine power.