Video Summary - Is A Head-On Collision The Same As Hitting A Wall At Twice The Speed?

Main Ideas and Conclusions

The experiment revisits Jamie’s earlier claim that two cars colliding head-on at 50 mph are equivalent to one car hitting a wall at 100 mph. Viewers argued that the head-on collision is instead comparable to a 50 mph wall impact.
The MythBusters tested the claim first with a small-scale model, then with full-size cars. The results supported the viewers’ argument: two identical cars each traveling at 50 mph and colliding head-on sustain damage and deceleration similar to one car hitting a solid wall at 50 mph—not 100 mph.
Although the cars approach each other at a combined closing speed of 100 mph, the impact is shared across both vehicles. In the tests, the head-on collision produced roughly the same G-load and vehicle deformation as the 50 mph wall crash.
The episode presents the result as consistent with Newton’s third law: each car exerts an equal and opposite force on the other. The test also shows why the closing speed between vehicles should not be confused with the impact speed experienced by either car compared with a rigid wall.
Jamie acknowledges that his original statement was wrong and says that correcting it is part of learning through testing.

A swinging weight represented a car, and a heavy steel block represented an immovable wall.
The team swung the weight at a baseline speed (“1x”) and at double that speed (“2x”), using clay to compare the impacts.
They then replaced the wall with a second, identical weight and collided the two at 1x.
The clay from the two-weight collision resembled the 1x wall-impact sample much more than the 2x sample. The team noted that the clay was useful for broad comparisons, but not precise measurements.

The team used identical cars and a track-and-cable system to propel them into a solid steel wall.
Accelerometers and a data logger recorded the cars’ deceleration.
In the 50 mph wall test, the car registered an average of about 58 Gs and shortened from 15 feet to about 11 feet 7 inches.
In the 100 mph wall test, the car was much more severely crushed, shortening to about 8 feet. The recorded peaks were 140 Gs and 230 Gs; the team cited a midpoint of roughly 185 Gs.
These benchmark crashes demonstrated that doubling speed caused substantially more severe damage and deceleration—not simply twice the damage.

Two identical cars, each about 1.5 tons, were sent toward one another at 50 mph.
The resulting wreckage looked similar to the 50 mph wall-test car and unlike the 100 mph wall-test car.
The cars recorded average loads of about 52 Gs and 58 Gs, close to the 50 mph wall test. Their final lengths were also similar to the 50 mph wall-test result.

Adam Savage — Co-host; explains the experiments and gives a prediction about the results.
Jamie Hyneman — Co-host; discusses his original claim and the test findings.
Narrator/voice-over — Provides transitions and explanatory commentary.
Test-facility crew/technicians — Assist with the crashes and report data. The subtitles name Mike, Hector, and Bob, though they do not consistently identify who is speaking.
Fans and physics-minded viewers — Challenge Jamie’s original claim, including with an argument invoking Newton’s third law.