The original Tacoma Narrows Bridge collapsed on November 7, 1940, just barely over four months after it was opened to the public. It is considered to be a prime example of failed engineering. It was a very long, very thin bridge without the needed girders for support underneath (fortunately, the remodeled version is still going strong). The common explanation for the Tacoma Narrows Bridge collapse is what is known as forced resonance. Explain, in your own words, what forced resonance means in this situation.