Watch this teacher's classroom 'experiment' go awry

Teacher tries to give lesson by showing effect of an axe on a cinder block, but misjudges swing, bringing tool directly into fellow teacher's groin.

This video captures the stomach-churning moment a physics teacher swings an axe into his co-worker's genitals - in a disastrously misjudged class experiment.

The nauseating footage was captured on a camera phone at a school in Portland, Oregon, and shows the well-built man lecturing a crowd of students before excitedly asking 'everybody ready?'.

The teacher then orders the class to give him a count as he hoists the axe up over his head and swings it directly into the unlucky fellow-teacher's crotch - causing him to squirm violently on the floor.

The idea of the experiment appears to be to crack open a cinder block that is balancing on the chest of one of his co-workers using the blunt end of the axe.

Standing with his legs astride over the teacher, he swings the tool over his head but completely misses his target.

The man appears to be wearing face protection but has not thought to cover his groin area and is seen writhing on impact just before the 17-second clip cuts out.

Uploaded to YouTube, the video has been titled: 'How the physics teacher lost his job.'

However, teenager Haneef Mubarak says nobody was fired - and remarkably the teacher who was hit turned out OK.

Mubarak, who says he is a student in the class, posted a second video and revealed that the unfortunate man holding the cinder block was actually the teacher of the AP Physics class at a high school in Portland.

The new clip shows the teacher with the axe actually take a second swing at the block, even as his coworker writhes in pain on the floor.

The teacher is actually holding the cinder block on his check on top of a bed of nails.

The experiment was meant to show that the nails would not pierce the teacher because the force was evenly distributed, Mubarak wrote on Reddit.

The new video shows the teacher get up and dust himself off. He appeared to have more pain in his chest, where he took the second hit, than his in groin.

'He got up and resumed teaching after the demo was over. Looked uncomfortable, but ya gotta do what ya gotta do,' Mubarak said.

- Daily Mail