This one was hilarious :
An engineer, a mathematician, and a physicist are each sentenced to die by the guillotine. As the physicist is led to the guillotine, he decides that he’d like to observe the blade as it falls, perhaps to verify v=at, and he requests to be strapped in face up. The executioner agrees (why not? it all pays the same…), and straps him in. As the blade falls, it sticks about two thirds of the way down. Seeing this, the crowd cheers - the physicist must be innocent! So the executioner unstraps him and sets him free.
The mathematician is next. Being well versed in matters (perhaps he is an actuary), he quickly asks to be placed face up as well - after all, the odds of it happening again are pretty good, especially if the initial conditions are similar. So the executioner obliges, and once again, the blade sticks about two thirds of the way down. Again the crowd cheers, and the mathematician is also set free.
Finally, the engineer. Not willing to do anything in public that is different from his peers, he also requests to be placed face up. As the executioner is strapping him in, he’s looking up at the blade and studying the track in which it slides. As he does so, he notices something. “Do you see that?”, he asks. “About one third the way up? If you fixed that there…