Here's why:
* Short vowel sounds are typically represented by a single vowel letter. In "shook", the "oo" is pronounced with a short "u" sound, similar to the "u" in "cup".
* Long vowel sounds are often represented by a vowel letter followed by a consonant, a second vowel, or a silent "e" at the end of the word.
Therefore, "shook" does not have a long vowel sound.