“I remember my grandma’s old Buick. That thing was built like a tank. You could hit a tree and barely leave a dent and drive away. These new cars just fall to pieces.” In my case, I usually hear this from my father-in-law, when defending his own elderly Buick ownership.
And to some degree, he is correct. Newer cars can be totaled at lower speeds, but it is on purpose. For the 50th anniversary of the creation of the Insurance Institute for Highway Safety, they staged a test to demonstrate how much car crashes have changed in that time (Warning: a very lovely car was destroyed to make this point).
Watching the video, your nostalgic friend/relative seems right about those old cars. The Bel Air comes out of the collision looking much more intact than the Malibu. The dummies, on the other hand, tell the real story. The Malibu driver gets out of the wreck with a broken ankle. The Bel Air driver is mostly likely dead, or permanently disabled. The failure of the car is what saves the driver’s life, with the energy of the crash largely expending deforming the metal, rather than being transfered to the driver.
Cars are hardly the only thing designed to fail. Certain styles of safety valves are designed to rupture before a pressurized tank would explode. For things like liquid nitrogen tanks, there is a standard release valve, like you’d find on a hot water heater, but there’s also a secondary burst disk in case the release valve isn’t working correctly. If you manage to prevent safe pressure release, the results could look something like this episode of Mythbusters:
On the other hand, with a faulty relief valve and a burst disk, you instead get a large pop, a very loud hissing until the tank has evacuated enough pressure, and you get to keep your building intact (though you may severely startle the grad students in the next lab over…).
When else is failure a good thing?
Thanks to bsabarnowl for the Buick picture!