A professor was dissatisfied the lack of effort his students were putting into his assignments, so his friend suggested to him that perhaps he might be able to hypnotize his students into working harder. 

"And just how would I go about doing that? " he asked. "It is very simple. First you turn off the air conditioner so that the lecture theatre is warmer than usual. Then you lecture in a monotone voice. Meanwhile, you dangle a watch on a chain and swing it in a slow arc above the podium and suggest they study harder & work harder for this module. 

"So the very next lecture, the professor did as suggested, and lo and behold, all the students submitted thoroughly researched and well written essays for the subsquent assignment. 

Now, the professor could not wait to try this again to ensure his students excel in the upcoming finals, so he tried it out on the next lecture. Just as the last of his students was becoming mesmerized, the chain on the watch broke and the watch hit the podium with a loud thud and springs and parts flew everywhere. "Crap! " exclaimed the professor. 

It took them a week to clean up the lecture theatre."