1. 1 Steel balls Topic 3 Taiwan Representative

2. 2 Outline Question Experimental set up: Vertical collision Materials: Paper, Plastic, and Metal sheets Experimental results: Hole size v.s materials, height… What we learned & discussion Conclusion

3. 3 Question Colliding two large steel balls with a thin sheet of material (e.g. paper) in between may "burn" a hole in the sheet. Investigate this effect for various materials.

4. 4 Experimental Setup: vertical collision 1 m H Sheet

5. 5 Materials 1. Paper (Burning point: 130 o ~232 o C) Reference:http://wiki.answers.com/Q/What _is_the_Burning_point_of_paperhttp://wiki.answers.com/Q/What _is_the_Burning_point_of_paper 2 mm 5 mm

6. 6 Inflammable materials Paper A thin piece of material left on the ball Greatly heated Burned O2O2 Greatly heated Burned O2O2

7. 7 Materials 2. Plastic (Melting Point: 106~114 ℃ ) (Soften temperature: 80~98 ℃ ) 3 mm 4 mm

8. 8 Non-flammable materials Plastic Compressed Into thin layer Melted Wrinkles Cooled down

9. 9 Materials 3. Aluminum foil (Melting point: 660  C) 5 mm 6 mm

10. 10 Non-flammable materials Aluminum foil Concentric circles wrinkles Melted Compressed

11. 11 Materials 4.Copper foil (Melting Point: 1083.0 °C) Reference:www.chemicalelements.com/elements/cu.html 5 mm 2mm

12. 12 Non-flammable materials Copper foil Concentric circles wrinkles Depends on condition Compressed Melted ??

13. 13 H PlasticPaper  = 7.6 cm

14. 14 Height v.s. Materials

15. 15 Height v.s. Materials

16. 16 Height v.s. Materials

17. 17 Height v.s. Materials

18. 18 Estimation of physical parameters during collision The highest temperature T max. = ? Duration ∆t = ? Collision area A=? Average pressure P = ? Conducted heat ∆Q = ? Adiabatic process? i.e. ∆W >> ∆Q

19. 19  We can melt Al foil. Melting point of Al = 660 ℃. T max. = ? Cooled after melted

20. 20 Duration ∆t = ? Our high speed video: 230 μs/frame

21. 21 Material t=0 Dropping ball Fixed ball Edge of pillar

22. 22 t=230μs Material Dropping ball Fixed ball Edge of pillar

23. 23 t=230μs x 2 Material Dropping ball Fixed ball Edge of pillar

24. 24 t=230μs x 3 Material Dropping ball Fixed ball Edge of pillar

25. 25 Duration ∆t = ? 1. Our high speed video: 230 μs/frame  ∆t < 230 μs 2. From reference our m ball =287 g R. Hessel, A. C. Perinotto, R. A. M. Alfaro, and A. A. Freschia, Am. J. Phys. 74 3, 176 (2006). We can conclude : ∆t < 230 μs

26. 26 Collision area A=? Al foil Diameter ~ 1.6 mm Estimate A from the melted Al foil. Diameter: 1.58± 0.08 mm

27. 27 Average pressure P = ? m=287 g, H=50 cm, g=9.8 m/s 2, A< π (0.8mm) 2, ∆t < 230 μs

28. 28 Work ∆W=? Pressure P > 1.2 x 10 9 Nt/m 2 Collision Area A= π r 2 ~ 2x10 -6 m 2 Thickness of sheet ∆d= 10 -4 m Conducted heat ∆Q=? ∆T < 1000 ℃ A= π r 2 ~ 2 x 10 -6 m 2 Air0.026 Al237 Cu401 Fe80.4 Steel46 Water0.61 Wood0.11 σ

29. 29 Heat produced Using the lowest production of work, Increase ofΔT, => Higher than melting point of Al: 660

30. 30 Adiabatic process?? Work done during collision ∆W > 3.9 ×10 -1 (J) Heat conducted during collision : ∆Q < 2.9 ×10 -4 (J) ∆W >> ∆Q  Adiabatic process T high T low

31. 31 Conclusion Height: Diameter of holes increases as height increases Collision Area:  Burning  Melting

32. 32 Colliding process P T

33. 33 Burning O2O2 O2O2

34. 34 Melting

35. 35 Conclusion Height: Diameter of holes increases as height increases Collision Area:  Melting  Burning Adiabatic Process is the main reason holes are burned because:  Δt is small  Area is small  Pressure is high

36. 36 Conclusion Height: Diameter of holes increases as height increases Collision Area:  Melting  Burning Adiabatic Process is the main reason holes are burned because:  Δt is small  Area is small  Pressure is high