44. Power 45. Mechanical advantage 46. Time 47. Watts 48. Fulcrum 49. Compound machine 50. Screw 51. Energy 52. KE=1/2mv^2 53. Potential energy 54. Kinetic energy 55. Mechanical energy 56. Non- mechanical 57. Chemical energy 58. Photosynthesis 59. Nuclear fusion 60. Open system 61. Open system 62. Efficiency 63. Heat