Transcript Krazy Glue
Is this really possible? B reaking down the physics of the krazy glue bungee jump using a stopwatch and some assumptions Approach: •Observe the “test jump” in the Krazy Glue video • time the acceleration (free fall) • deceleration (slowing down) portions of the test jump. •Using the times for the free fall and slowing down portions of the jump, and some assumptions about the weight of the jumper, calculate the force and stress on the bonded coupling. Assumptions: •Jumper weighs 150 lb •Neglect wind resistance •Diameter of the bonded coupling = 2 inches •The bungee cord behaves like a perfect spring, and has a constant spring constant throughout its range of motion. •The bonded coupling is only under load during the deceleration portion of the jump Bungee Jump Schematic Jumper Bridge Bonded coupling Tf = Free Fall Time Bungee cord Ts = Slow Down Time The Ground Times Jumper Bridge Bonded coupling Free Fall Time Tf = 1.19357sec Bungee cord Slow Down Time Ts = 1.23308sec The Ground calculating the force on the bonding coupling the force on the bonded coupling in the Krazy Glue bungee jump Formula Used: Newton’s second law of motion: F = ma + mg F = Force (this is the force on the bonded coupling that we’ll calculate) m = mass (this is the mass of the jumper – 68kg) a = acceleration (this is the rate of slowing down due to the bungee cord or “deceleration”) g = acceleration due to gravity (9.8m/sec2) Calculate the acceleration: (Initial velocity – final velocity) / slowing down time Vi = Tf x g = 1.193571sec * 9.8m/s2 = 11.697 m/s Vf = 0 Slow down time (Ts)= 1.233077sec a = 11.697m/s / (1.233077s) = 9.486026m/sec2 F = (m x a) + (m x g) F = (68kg * 9.486026m/sec2) + (68kg * 9.8m/sec2) F = 645.0498N + 666.4N F = 1311.4498N F = 294.8203614 lbs Stress = F / A Stress = 294.8203614 lbs / 3.14159in2 Stress = 93.844315 psi Surface Prep and Bonding •We prepped the surface of aluminum cylinders using a grit blaster as well as an acetone based solution. and bonded them together to form test coupons using and Krazy Glue. •We bonded together 7 different test coupons. They were bonded together using three different types of glue. We also tested how two of the different glues would behave when the surface was contaminated prior to bonding. •#1: Aircraft Grade structural bonded joint •Surface prep: grit blaster, phosphoric acid anodizing, and bond primer •Glue: 3M Scotchweld EC2216 •#2: Krazy Glue •#3: Krazy Glue •#4: Contaminated Krazy Glue •Contaminate: Cat Oil •#5: Boeing’s Krazy Glue •#6: Boeing’s Krazy Glue •#7: Contaminated Boeing’s Krazy Glue •Contaminate: Cat Oil Testing Results (psi) 1600 1400 Stress (psi) 1200 1000 800 600 400 93.844315 psi 200 0 Boeing Glue W/w/oil Oil Boeing Glue Boeing Glue Glue Boeing Boeing BoeingGlue Glue Krazy Glue Krazy Glue w/oil Krazy KrazyGlue Glue W/ Oil Glue 3m Scotchweld EC 2216 Krazy Glue 3M Scotchweld EC2216 Krazy Glue