The end of a stopped pipe is to be cut off so that the pipe will be open. If the stopped pipe has a total length L, what fraction of L should be cut off so that the fundamental mode of the resulting open pipe has the same frequency as the fifth harmonic (n = 5) of the original stopped pipe?
Express your answer in terms of L.

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

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At what time will the interfering waves have an amplitudeof zero?