The physics of Winter Olympic sports
Every Winter Olympics and Paralympics, we are treated to displays of incredible athleticism as competitors from across the world take to the snow and ice.
As athletes hurtle down ice tracks, soar into the air or glide across a sheet of ice, they are constantly battling against forces acting upon them.
It takes a great deal of skill, knowledge and preparation to minimise the impact of these forces, and the Olympic medallists will be those who are able to master them successfully. BBC Bitesize explores how they do it.
Curling
Curling is a team sport in which two teams must slide 19.1kg (44lbs) granite stones down a sheet of ice over 45m long, to a large target area known as the house. The teams’ aim is to have their stones closest to the centre of the target, out-counting any opposing stones, at the end of each end.
Curling takes its name from the way the stones behave as they travel down the ice, curling either inwards and outwards. Players can control the direction of curl by applying a clockwise or anti-clockwise rotation on the stone as they release it.
Curling stones are only able to travel the length of the sheet because of how the ice has been prepared. It may appear perfectly flat, but get closer and you’ll notice that the ice is actually covered in lots of tiny bumps, known as the pebble. Ice technicians spray the surface of the ice with water droplets which then freeze. These bumps reduce the surface area of ice in contact with the bottom of the stone, therefore reducing the amount of
acting on it.
Sweepers can force a stone to travel further or influence how much it curls. By applying downwards pressure through their brushes, and moving them with a high stroke rate, they generate heat and begin to melt the pebble, leaving a thin layer of water in the path of the stone which creates less friction. Strong sweepers with good technique can get a stone to travel several metres further than it would have travelled without assistance.
In wheelchair curling, there are no sweepers to help finesse the shot and so players must be as accurate as possible when delivering their stones.
Ski jump
For ski jumpers, the goal is to jump as far as they possibly can while holding their body in the perfect position to secure style points from the judging panel. Distance measurements are taken from the K-line, which takes it name from the German word ‘kritisch’, meaning critical. Points are added for every metre an athlete travels over the line, and deducted for every metre they fall short.
As ski jumpers launch themselves down the ramp (the in-run), the effect of Earth’s gravity means that their speed increases. However, they also lose speed to the combined forces of friction and
, and so have to find ways of minimising their impact.
Friction between the skis and the ice itself can slow a ski jumper, so hot wax is applied to the skis to give them a smoother finish. The wax used varies according to the weather conditions.
To combat air resistance, a ski jumper will adapt their body position. By bending their knees and extending their arms behind them, they are able to reduce their body surface area, giving the air resistance less to act on.
Once in the air, it’s a completely different story. Ski jumpers want to make their body surface area as big as possible in order to take advantage of lift. Lift is a force which acts
to the flow of air around the athlete and the weight dragging them down, due to. It helps to keep them in the air by pushing upwards.
Most ski jumpers will position their skis to look like a V, as it is thought to be more efficient at producing lift than the alternative parallel position. Ski jumpers use skis that are longer and wider than traditional skis, up to 145% of the athlete’s height, further increasing their surface area.
Bobsleigh
In bobsleigh, teams of one, two or four athletes complete timed runs down a twisting ice track with steeply banked corners. Tracks are typically between 1,200m and 1,500m long, containing between 15 and 20 turns.
The only opportunity that bobsleigh athletes have to generate any useful force is right at the start of the race with the 50m push. It’s not unusual for track sprinters to switch disciplines to bobsleigh, as they often have the necessary explosive power to generate high
in a short period of time.
When jumping into the bobsleigh in a carefully choreographed manoeuvre, the athletes will focus on keeping it as straight and steady as possible so as not to waste energy through sideways movement.
Once in the bobsleigh, athletes must concentrate on conserving the force they’ve generated by minimising air resistance and friction. Equipment has a huge role to play in this, with bobsleighs having been carefully designed to be as light and aerodynamic as possible (within the specified weight restrictions). Athletes adopt a tucked position, allowing the air to flow smoothly over the top of them. Highly polished runners underneath the bobsleigh help to minimise friction.
Hitting the wall of the ice track slows down a bobsleigh, so the pilot/driver needs to judge the perfect line to take.
No comments