What happens when a knight on horseback slams a lance into his opponent at full gallop? According to a new study by physics students at the University of Leicester, the answer involves forces and energy levels comparable to a car crash.
Published in the Journal of Physics Special Topics, the article uses classical mechanics to model a typical medieval jousting encounter. Factoring in the mass of the horse, rider, armour, and lance, the authors estimate that a knight galloping at 13.4 metres per second (around 48 km/h) could transfer 1,030 newton-seconds of momentum and 53,000 joules of energy through his lance.
A Deadly Calculation
The authors model the knight as a single mass, combining the destrier (a 450 kg warhorse), an 80 kg rider, 29.3 kg of armour, and a 10 kg lance. The lance is assumed to be made of European ash, a wood historically used for weapons and tools.
To calculate the force delivered in a jousting strike, they consider the lance to be braced by a lance arrêt and saddle—devices that allowed nearly all of the momentum to pass through the lance tip upon impact. The result is a simplified inelastic collision where the lance either transmits the full force or breaks under stress.
The Numbers Behind the Blow
Using Newtonian mechanics, the team calculates that a knight and horse at full gallop generate 7,700 newton-seconds of momentum. If all that force were delivered in a 0.01-second window—a plausible but estimated value—the resulting impact would produce a staggering 153,000 newtons of force.
However, European ash has a limit: the lance can only withstand 103,000 newtons before breaking. This means that in most cases, the lance would shatter, transferring only the maximum amount it can sustain. Based on this, the authors estimate a momentum transfer of 1,030 newton-seconds and an energy transfer of 53 kilojoules.
How Much Energy? Think Honda Civic
To put 53 kilojoules into perspective: that’s about the same kinetic energy as a 1,300-kilogram car (like a Honda Civic) crashing into a wall at 28.5 km/h (17.7 mph). It’s also roughly equivalent to being struck by a 10-kilogram sledgehammer swinging at over 100 km/h. In other words, a jousting strike delivered a force that most people today would only experience in a serious accident.
Designed for Impact
The study sheds light not only on the brutality of jousting but also on the sophistication of medieval martial equipment. The combination of heavy plate armour, specialised saddles, and the lance stop meant that the knight could absorb and deliver incredible amounts of force in a controlled way. The lance itself, while sacrificial, played a crucial role in focusing and transferring energy.
While the authors note several simplifications—including treating the rider and horse as a single body and assuming an estimated impact time—the study provides a valuable look into the mechanics of medieval warfare. It highlights just how physically intense jousting really was, and why armour design, weapon construction, and controlled impact zones were essential in both tournaments and combat.
The article, “Knights In Shining Armour: The Joust,” by E. Whelan, D. Knight, B. Sampson, S. Wedge, appears in the Journal of Physics Special Topics. Click here to read it.
The Journal of Physics Special Topics is an undergraduate journal published by physics students at the University of Leicester. As part of a unique final-year module, students research and write short papers that apply real physics principles to imaginative or unconventional scenarios. Topics have ranged from the plausibility of lightsabers and the physics of superhero landings to the energy output of dragons and the survivability of falling from great heights. Each paper is peer-reviewed by fellow students and guided by faculty, offering an engaging introduction to academic publishing and scientific communication. Click here to read more of their articles.
Top Image: Photo by R’lyeh Imaging / Flickr
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