Here's why:
* The "a" in carpet is pronounced like the "a" in "father" or "car," which is a long vowel sound.
* Short vowels typically have a shorter, more clipped sound. Examples of short vowel sounds are in words like "cat," "bed," or "hot."
So, when you say "carpet," you're holding the "a" sound for a longer duration, making it a long vowel sound.