The Physics Behind the Ski Jump
Updated: Jun 18, 2022
By Rosalyn Brady
April 7, 2022
UPDATED 12:00 PM EST
[Photo Credit: Marked by Teachers]
Every four years, the Winter Olympics gathers incredible athletes to compete in a variety of sports. The Winter Olympics is the most renowned opportunity to witness many of these sports―including the ski jump, in which skiers ski down a steep ramp and attempt to achieve the farthest jump from the end of the ramp with the best form.
But have you ever wondered why we are able to watch the ski jump and why it works the way it does?
The answer is simple: the ski jump works due to the laws of physics that define it - from beginning to end.
At the beginning of the ski jump, the skier positions themself on a metal bar at the top of the ramp. This is where the physics begins―with the skier’s gravitational potential energy. All elevated objects have gravitational potential energy, which is converted into kinetic energy as the object falls. It is the same as the skier travels down the ramp: they convert the gravitational potential energy they have at the top of the ramp into kinetic energy as they ski downwards.
After release, the skier interacts with the forces of drag (air resistance), gravity, and lift. Lift is an upward force that is generated when air particles push upwards on an object that is pushing down on the particles―it is a reaction force to the skier’s downward force. This occurs due to Newton’s Third Law, which states that every force is met with an equal and opposite reaction force. If the force of lift is greater than that of gravity, then lift will surpass gravity and the skier will be airborne. Therefore, the goal is to maximize lift, thereby maximizing the amount of time the skier is airborne.
Before that, while skiing down the ramp, the skier must still minimize air resistance so that they can build up maximal momentum and speed for takeoff. To do this, skiers crouch to minimize the amount of surface area of their body in contact with the air. They also must steer carefully to minimize the amount of friction―resistance to movement―their skis experience. Additionally, skiers wear smooth, aerodynamic helmets and maintain a streamlined position with their arms behind them, to allow air to pass over their bodies more easily, until they reach speeds as high as 90 km/hour.
The ramp ends in a downward angle of 10 degrees. Skiers extend from their crouch and attempt a perfectly-timed jump to maximize flight time―after which they must maximize lift instead.
To do this, they use their flat-positioned body and long skis 145% of their height to push downwards on the air and maximize the amount of surface area of their bodies and skis doing so, because more air experiencing a downward force means more air to push back and generate lift. Skiers also wear tightly-fitting microfiber suits that do not allow air to permeate, instead forcing the air to pass over the skier and generate more lift, and they position their skis in a V shape slightly wider than their body and hold their arms slightly away from their torso, with their body and skis nearly perfectly parallel to the ground. This position maximizes the amount of surface area of the skier’s body in contact with the air, and provides the optimal angle of attack―which is the angle at which the wind meets an airborne object―in this case, the base of the skis; the optimal angle of attack for the ski jump is 20-25 degrees―to generate the most lift possible.
From here, skiers contend with weight, or gravity, and air resistance, or drag. These are inevitable forces, but are mitigated with things such as especially lightweight skis. The air resistance, which opposes the skier’s motion, and the Earth’s gravity, pulling them downwards, gradually slow the skier down until they finally land, once more on the ground.
References
“Falling with Style: The Science of Ski Jumping.” Smithsonian Science Education Center, 1 Feb. 2018, ssec.si.edu/stemvisions-blog/falling-style-science-ski-jumping.
https://ssec.si.edu/stemvisions-blog/falling-style-science-ski-jumping
Magazine, Smithsonian. “The Freaky Physics of Ski Jump.” Smithsonian Magazine, 11 Feb. 2022, www.smithsonianmag.com/science-nature/the-freaky-physics-of-ski-jump-180979554.
https://www.smithsonianmag.com/science-nature/the-freaky-physics-of-ski-jump-180979554/
2373. “What Is Air Resistance?” Universe Today, 17 May 2016, www.universetoday.com/73315/what-is-air-resistance.
https://www.universetoday.com/73315/what-is-air-resistance/
Kivekas, Juha and Mikko Virmavirta. “Aerodynamics of an Isolated Ski Jumping Ski.” SpringerLink, 2016, link.springer.com/article/10.1007/s12283-019-0298-1#:~:text=Almost%20all%20studies%20of%20V,around%2025%C2%B0%E2%80%9330%C2%B0.