A What Machine?
In my English class at the college, I explained washers and dryers to my students. They nodded then looked down at their notes. After a long pause, one brave soul raised his hand and asked, "Would you please explain that again?" So, I explained it again. And again. And again. The students listened with furrowed brows. The issue, I think, was not that they didn't understand it - they just didn't believe me. It took a few minutes, and many questions (Where does the water come from?) until their faces began to relax.