Physics jokes are more likely to make you groan than laugh. I have lost count of the many times I have heard a pupil say "But sir, it isn't funny!". Nevertheless, I have included a few below, which I have created using GoAnimate - if you haven't come across this before then I strongly recommend you take a look: I've had lots of fun recently getting pupils to use it to put together Physics related animations as end of year projects. It's quick to use and very simple!
A neutron walks into a bar...
Another neutron walks into a bar... or does it?