The Doppler shift was first tested in 1845by the French scientist B. Ballot. He hadatrumpetplayersounda434Hznotewhi leriding on a flat-car pulled by a locomotive. Atthe same time, a stationary trumpeter playedthe same note. Ballot heard 7 beats/s. How fast was the train moving toward him

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.

a

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