Please Don’t Ban My Concrete Block Smashing Physics Demo From Schools

Dear school administrators, parents, politicians, OSHA, and lawyers:

By now you’ve probably seen the viral video below of a concrete block smashing Physics demo gone wrong* (WARNING: disturbing content.) As a veteran Physics teacher who does this demonstration in classes several times a year, both as the “smasher” and as the “smashee,” I am assuming that you are about to walk down to my office, email me, or draft a law telling me that I can never perform such a dangerous demonstration in my classroom ever again. Please don’t. You shouldn’t. Here’s why.

1. From a Physics education standpoint, the demonstration is very valuable.

The cinder block smash is a classic demonstration of inertia and conservation of energy, two of the most important principles in introductory Physics. The large energy of the swinging sledge hammer is dissipated into the cinder block in via kinetic, thermal, and other forms of energy, rather than being transferred (painfully) to the person lying on the ground. Furthermore, the inertia of the massive cinder block prevents the block from experiencing any significant acceleration downward into the the smashee’s chest. Done correctly, the most uncomfortable aspect of this demonstration is merely the weight of the cinder block resting on your trusted colleague prepares to swing. The actual impact feels no more significant that a friend’s good-natured punch in the arm. When safely executed (see video of me performing the stunt at the bottom of this page), the demo is a powerful and memorable experience for the students. As a class, we are able to connect back to this demo throughout the year as we touch on energy and inertia. And when I cross paths with former students who have grown up and moved on, they often remark that they remember the demonstration vividly and that the associated —> Read More