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彈性碰撞現象介紹

彈性碰撞現象介紹. 趣味科學實驗 科廣系 葉聰文. 碰撞過程. 小時候，我們會玩泥巴球遊戲，比比看誰的泥巴球比較硬 。 當上面的泥球落到下面的泥球上，兩個泥球就發生所謂「碰撞」。 結果，有一顆泥球破了。這表示另一顆沒破的泥球比破掉的泥球還硬。. 碰撞過程. 另外 ， 當我們在平地上拍著籃球或皮球 ， 會比比看誰拍的次數玩泥巴球遊戲 。 遊戲可持續是因為，籃球與地面發生了「碰撞」。 籃球遊戲中球會彈起來 ， 但泥球遊戲中泥球卻不會，同樣是「碰撞」現象，兩者有何不同呢？. 碰撞現象. 遊戲 : 撞球遊戲、各種球類運動、氣墊球等。

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彈性碰撞現象介紹

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  1. 彈性碰撞現象介紹 趣味科學實驗 科廣系 葉聰文

  2. 碰撞過程 • 小時候，我們會玩泥巴球遊戲，比比看誰的泥巴球比較硬。 • 當上面的泥球落到下面的泥球上，兩個泥球就發生所謂「碰撞」。 • 結果，有一顆泥球破了。這表示另一顆沒破的泥球比破掉的泥球還硬。

  3. 碰撞過程 • 另外，當我們在平地上拍著籃球或皮球，會比比看誰拍的次數玩泥巴球遊戲。 • 遊戲可持續是因為，籃球與地面發生了「碰撞」。 • 籃球遊戲中球會彈起來，但泥球遊戲中泥球卻不會，同樣是「碰撞」現象，兩者有何不同呢？

  4. 碰撞現象 • 遊戲 : 撞球遊戲、各種球類運動、氣墊球等。 • 日常現象：汽車相撞、走路互撞、球場上球員相撞等。 • 天文現象：隕星撞地球、隕星撞擊木星、月球上的坑洞等。 • 微觀現象：分子碰撞、布朗運動、原子撞擊 • 人為實驗：透過碰撞過以促使次反應發生，如分子對撞機研究化學變化機制、粒子對撞機研究次原子結構。

  5. 動量與動量守恆

  6. 動量 • Q1：大卡車與小汽車以相同速率行駛，何者動量大？ • Ans：大卡車，因其質量較大。 • Q2：一部大卡車與一隻輪式溜冰鞋自山坡上往下滑時，何時溜冰鞋的動量會比大卡車大？ • Ans：當溜冰鞋的速率遠大於大卡車的速率時。 • Q3：動量的單位如何定？ • Ans：公斤公尺/秒。

  7. 衝量 • 物體動量的改變量稱為衝量。 • 施力越大，物體的加速度越大，亦即速度的改變量越大，如此動量的改變量也愈大。 • 欲達到相同的動量改變量，施力的大小與施力時間長短成反比。 • 衝量＝施力X時間＝動量的改變量

  8. 衝量-實例 • 高爾夫球選手開球或棒球打擊手擊球時的拉球動作。 • 增加球桿或球棒與球接觸的時間。

  9. 衝量-實例 • 若你坐在一部失控的汽車上，現在要讓此車停下來，而只有兩種方式可以選擇：堅硬的水泥牆或柔軟稻草堆，你會選擇哪一種？為什麼？

  10. 衝量與反彈 • 讓物體停止並在反彈回去所需要的衝量，比僅讓物體停下來，需要更大的衝量。

  11. 動量守恆 • 在沒有外力作用下，一個系統的動量保持不變。 • 例：你坐在車內使勁地推儀表版，車子會動嗎？ • 例：步槍發射子彈，步槍會後退，子彈往前飛，步槍與子彈的動量合是否有改變？

  12. 碰撞 • 在沒有外力作用下，兩物體發生碰撞，碰撞前後兩物體的淨動量相等。 • 彈性碰撞：當物體間的碰撞沒有造成永久形變或產生熱。 • 非彈性碰撞：若碰撞過程中，造成物體發生形變或有熱的產生。

  13. 彈性碰撞 • 彈性碰撞：當物體間的碰撞沒有造成永久形變或產生熱。

  14. 彈性碰撞

  15. 非彈性碰撞 • 非彈性碰撞：若碰撞過程中，造成物體發生形變或有熱的產生。

  16. 非彈性碰撞

  17. 非彈性碰撞

  18. 非彈性碰撞

  19. 非彈性碰撞

  20. Hierarchy of structure R ~ 10-15 m (strong) R ~ 10-10 m (electromagnetic) R > 106 m (gravitational) CERN - Particles, Fields and the Big Bang

  21. Why accelerate particles (2) E = mc2 : “Mass is condensed energy” concentrate energy on one particle Photons ------ Creation of new particles CERN - Particles, Fields and the Big Bang

  22. Particles from energy More energy - more (and new) particles are created CERN - Particles, Fields and the Big Bang

  23. u e e d  c  s t   b 3 FAMILIES - out of the vacuum Leptons Quarks Family 1 (light) Family 2 (heavy) Family 3 (v. heavy) WHY 3 FAMILIES ?? CERN - Particles, Fields and the Big Bang

  24. CERN 2300 employees (-> 2000) 6000 visitors 20 Member states + US, Canada, Japan, Russia, China, India, ... Accelerators (LHC, 2007) Detectors (Atlas, cms, lhcb, alice) 27 km CERN - Particles, Fields and the Big Bang

  25. CERN accelerators CERN - Particles, Fields and the Big Bang

  26. LHC tunnel, magnets Proton-proton collisions E = 7000 + 7000 GeV 800 million collisions/sec Largest cryogenic system (1.8 K, suprafluid helium) 27 km of 8 T magnets 100 m below surface CERN - Particles, Fields and the Big Bang

  27. Particle collisions CERN - Particles, Fields and the Big Bang

  28. Installation of ATLAS detector CERN - Particles, Fields and the Big Bang

  29. Installation of CMS detector Lhc pushes frontiers of: -detector technology • data transmission • Computing power CERN - Particles, Fields and the Big Bang

  30. The ‘Higgs’ field How do particles get their ‘inertia’ ? THE “CELEBRITY AT PARTY” MODEL (quarks or leptons) THE “rumour” model (Higgs particle) Particle Mass determined by strength of interaction with higgs field CERN - Particles, Fields and the Big Bang

  31. Search for the ‘Higgs’ field Higgs field particle “decays” into lepton (or quark) pairs according to their mass LHC Only 1 higgs in 1,000,000,000,000 events CERN - Particles, Fields and the Big Bang

  32. What is the Vacuum? • ‘Recipe’ for particles and fields • Quantum fluctuations • Lamb shift • Casimir effect • “Vacuum energy” • 1094 GeV/cm3 ??? • measured: < 10-5 GeV/cm3 WHY is vacuum so empty? CERN - Particles, Fields and the Big Bang

  33. Before the Big BANG ? The primordial vacuum: 1094 GeV/cm3 ? CERN - Particles, Fields and the Big Bang

  34. BIG Bang - eras 380,000 yrs atoms 10-10 ... 1 sec particles 10-32 sec “big bang” BB ~10-34 sec: inflation < 10-43 sec: Planck era CERN - Particles, Fields and the Big Bang

  35. Big Bang - Successes • Cosmic expansion (Redshift) • Age of cosmic objects • less than ~ 12-13 billion yr • Sun ~ 4.7 billion yr • Universal Ratio H:He ~ 3:1 • Snapshot at t ~ 3 min • Strong constraint on matter density • Cosmic Microwave Background (CMB) • Snapshot of Universe at t ~ 380,000 yrs CERN - Particles, Fields and the Big Bang

  36. Big Bang - MYSTERIES What caused inflation? Vacuum energy? How did the initial symmetry break? Hierarchy of interactions? Mass of particles? Where has the antimatter gone? CERN - Particles, Fields and the Big Bang

  37. Antimatter in the Universe ? Cosmic antiparticles ? Balloons Alpha Magnetic Spectrometer Radiation from matter-antimatter boundaries ? Radiotelescopes Gamma-Ray Satellites CERN - Particles, Fields and the Big Bang

  38. Antimatter research at cern Antihydrogen hydrogen (antiproton + positron) (Proton + electron) ? = Are the Energy Levels identical ? Two Experiments at cern:ATHENA and ATRAP CERN - Particles, Fields and the Big Bang

  39. Antiproton Decelerator at cern CERN - Particles, Fields and the Big Bang

  40. Antimatter research at cern 1) Production of antiprotons (v ~ c) 2) Deceleration (v ~ 0.1 c) 3) Capture + cool in ‘Penning trap’ 4) Mix with positrons 5) Create and detect antihydrogen CERN - Particles, Fields and the Big Bang

  41. Antimatter research at cern ATHENA experiment produced ~ 106 antihydrogen atoms Observed by annihilation products (‘post mortem’) CERN - Particles, Fields and the Big Bang

  42. Future of Antimatter Research Precision spectroscopy: E/E < 10-15 Gravitational measurements CERN - Particles, Fields and the Big Bang

  43. Cosmic microwave background Our Universe is filled with photons from the time of atom formation (380,000 yrs). They were produced during the BIG BANG. Their energy distribution and inhomogeneity give information about the age and composition of the universe. Microwave Anisotropy Probe Courtesy: NASA/WMAP CERN - Particles, Fields and the Big Bang

  44. Cosmic Microwave background Temperature Distribution on earth (for comparison) T/T ~ 0.3 T/T ~ 3·10-5 Temperature Distribution In Universe Courtesy: NASA/WMAP CERN - Particles, Fields and the Big Bang

  45. Cosmic Microwave background FIT observation with BIG BANG MODEL - Inflation stretches ‘quantum ripples’ Light element synthesis (matter) Dark (=non-baryonic) matter Age and shape of universe Courtesy: NASA/WMAP CERN - Particles, Fields and the Big Bang

  46. Cosmic Microwave background Stars and Planets only account for a small percentage of the universe ! CERN - Particles, Fields and the Big Bang

  47. Evidence for dark energy Evidence No. 1 - Cosmic Microwave background Evidence No. 2 - Expansion history of universe Large scale study of old supernovae COSMIC EXPANSION SPEED INCREASES! Driven by ‘dark energy’ CERN - Particles, Fields and the Big Bang

  48. Mystery: “dark energy”? vacuum energy Quantum fluctuations of fields Inflaton The field that drove the initial expansion Higgs field The field that gives mass to particles Einstein’s “cosmological constant” The field needed to balance gravitational collapse of the universe CERN - Particles, Fields and the Big Bang

  49. MORE Evidence for “dark matter” Galactic rotation curves (velocity of stars in periphery far too high) CERN - Particles, Fields and the Big Bang

  50. Evidence for “dark matter” gravitational Lensing (LENSING MUCH STRONGER THAN EXPLICABLE WITH VISIBLE MASS) CERN - Particles, Fields and the Big Bang

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