Year 9 STEM Club The Skeleton Luge

CHALLENGE Make a model of a bob skeleton sled See how far you can launch a Barbie! Present an answer to the question: Athlete or Machine? Which is more important in the sport of bob skeleton?

Session plans Week 1 – Intro and start building Week 2 – Finish building and test Week 3 – Competition – Distance and Speed Week 4 – Athlete or Machine?

Week 1 Introduction to the task Video Meet Barbie Each team given resources and drilling template Start building

Make a 1:5 bob skeleton sled Make the runners by bending the metal rod Attach runners to pod with cable ties Make sled’s launch tube using acetate sheet, tape and a plastic nose cone (check that it fits onto the pump’s launch tube) Fix the launch tube to the pod with double-sided sticky pads

Drilling template

Week 2 Continue to build Start testing the launch Redesigns and refinements

Launch the model bob skeleton sled. Launch Barbie!

Week 3 Competition time Distance with and without Barbie Speed with and without Barbie Timing gates

Extension Set up timing gates to measure the speed of the sled with and without the Barbie.

What factors are going to affect the speed at which Barbie travels? What factors are going to affect the speed of the real Skeleton Luge on an ice track?

Factors Weight The athlete’s shape The athlete’s position Aerodynamic lift Steering Clothing and equipment Starting Corners Ergonomics (how the body fits a product) Track incline (the slope down the length of the track) Friction on the ice Aerodynamic drag (air resistance) Tuning the characteristics of the skeleton Material choice Sled runners

Week 4 Athlete vs Machine Use calculations to work out which element of the luge/athlete partnership is the most influential to its success. Summary and extension

Potential Energy (PE) = m x g x h Change in PE for our athlete and sled = Joules (J) Kinetic Energy (KE) = ½ x m x v x 97 kg x (40.23 x 40.23) = J Amy Williams max speed Max speed if all PE transferred into KE Mass (m) of athlete and sled = 97kg Vertical drop of track (h) = 152m 1450m (diagram not to scale) Gravity (g) = 9.81 m/s 2 Energy transfer Why isn’t the all of the athlete’s and sled’s potential energy transferred into kinetic energy?

Calculating friction force F f =  x m x g F f = …………………………  =Mu, the coefficient of friction (steel on ice = 0.03). m =Mass (kg). g =The acceleration due to the gravity, which is 9.81 m/s 2. What is the friction force acting on the runners of a bob skeleton sled and athlete with the combined mass of 97 kg (athlete = 68 kg, sled = 29 kg)?

Calculating drag force F DRAG = ½ x  x C D x A f x V 2 F DRAG = ………………………….  =1.2 kg/m 3 (density of air) C D =0.45(drag coefficient of athlete and sled) A f =0.139 m 2 (frontal area of athlete and sled) V =40 m/s(velocity) Calculate the drag force acting on the athlete and sled as they travel down the track at 40 m/s?

What is the total force resisting the forward movement of the athlete and her sled down the track? F TOTAL = …………………………………… Between which velocities is friction force dominant? ……………………………………………….. Between which velocities is drag force dominant? ……………………………………………….. You can compare the two forces on the graph here Speed in metres/second (m/s) Force in Newtons (N)

Prove that it is better to be heavy and narrow when competing in The sport of bob skeleton. ATHLETE 1 Total mass: 97 kg A f : m 2 ATHLETE 2 Total mass: 100 kg A f : m 2

Athlete or Machine? Which is more important in the sport of bob skeleton? Discuss this question with your partner/team Present your answer to the rest of the group

Summary and Extension