Presentation on theme: "Athlete or Machine? www.raeng.org.uk/athleteormachine Presented by Dominic Nolan. The Royal Academy of Engineering."— Presentation transcript:
1Athlete or Machine? www.raeng.org.uk/athleteormachine Presented by Dominic Nolan. The Royal Academy of Engineering
2Investigate the big question: athlete or machine? Practical activities and testingMathematics activitiesScience activitiesEngineer/athlete videoStudent ledIndependent investigationHigher level thinkingScheme of work for STEM day or STEM club
3Make a 1:5 bob skeleton sled 90 minute makeCheap materialsBasic tools and equipment
5Make some timing gates (if you have the time) Achieving launch pressure consistency
6Bob Skeleton 1500m track 150 m vertical drop 143 km/h (40 m/s, 89 mph) Athletes times differ by tenths of secondsRules for sled’s dimensions, mass and materials33 – 43 kg sledAmy Williams - Olympic gold 2010
7Which is more important in the sport of bob skeleton? CHALLENGEMake a model of a bob skeleton sledSee 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?
8Make a 1:5 bob skeleton sled Make the runners by bending the metal rodAttach runners to pod with cable tiesMake 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
9Launch the model bob skeleton sled. Launch Barbie!
10Factors Weight The athlete’s shape The athlete’s position Aerodynamic liftSteeringClothing and equipmentStartingCornersErgonomics (how the body fits a product)Track incline (the slope down the length of the track)Friction on the iceAerodynamic drag (air resistance)Tuning the characteristics of the skeletonMaterial choiceSled runners
12Potential Energy (PE) = m x g x h Kinetic Energy (KE) = ½ x m x v2 Energy transferPotential Energy (PE) = m x g x hChange in PE for our athlete and sled =Joules (J)Kinetic Energy (KE) = ½ x m x v20.5 x 97 kg x (40.23 x 40.23) = JMass (m) of athlete and sled = 97kgVertical drop of track (h) = 152m1450m(diagram not to scale)Gravity (g) = 9.81 m/s2Amy Williams max speedMax speed if all PE transferred into KEWhy isn’t the all of the athlete’s and sled’s potential energy transferred into kinetic energy?The line graph above shows that if all the potential energy (PE) were to be transformed into kinetic energy (KE) then the athlete and sled would need to travel at 55 m/s (122 miles per hour) to reach a KE figure of J.However, the 2010 bob skeleton Olympic champion, Amy Williams, is known to travel at a maximum speed of 90 mph (40.23 m/s).Our simple analysis of the energy transfer over estimates the maximum speed of the athlete and sled by 15 m/s or 37% because it neglects the affects of aerodynamic drag and friction.
13Calculating friction force Ff = x m x gFf = …………………………= 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/s2.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)?Ff = 0.03 x 97 x 9.81 = N
14Calculating drag force FDRAG = ½ x x CD x Af x V2FDRAG = ………………………….= 1.2 kg/m3 (density of air)CD = 0.45 (drag coefficient of athlete and sled)Af = m2 (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?FDRAG = 0.5 x 1.2 x 0.45 x x 1600 = N
15Speed in metres/second (m/s) Speed in metres/second (m/s) What is the total force resisting the forward movement of the athlete and her sled down the track?FTOTAL = ……………………………………Between which velocities is friction force dominant?………………………………………………..Between which velocities is drag force dominant?You can compare the two forces on the graph here.1020304050607080515253545Speed in metres/second (m/s)Force in Newtons (N)F TOTAL = N1020304050607080515253545Speed in metres/second (m/s)Force in Newtons (N)
16Prove that it is better to be heavy and narrow when competing in The sport of bob skeleton.ATHLETE 1Total mass: 97 kgAf: m2ATHLETE 2Total mass: 100 kgAf: m2ATHLETE 1Friction force = 0.03 x 97 x 9.81Friction force = NDrag force = 0.5 x 1.2 x 0.45 x x 1600Drag force = NTotal force acting against athlete and sled = NATHLETE 2Friction force = 0.03 x 100 x 9.81Friction force = NDrag force = 0.5 x 1.2 x 0.45 x x 1600Drag force = NTotal force acting against athlete and sled = NAthlete 2 should get to the bottom of the track quicker as there is less force acting against the forward motion of the athlete and sled.Increasing athlete mass does not have a significant impact on friction compared to effect of increasing frontal area.
17Which is more important in the sport of bob skeleton? Athlete or Machine?Which is more important in the sport of bob skeleton?Discuss this question with your partner/teamPresent your answer to the rest of the group