Work & Energy
Physics · कार्य और ऊर्जा · 16 facts
Work = Force x Displacement x cos(theta); unit = Joule (J); work is scalar
Work is zero if: no displacement, or force perpendicular to displacement (theta=90)
Positive work: force and displacement same direction; Negative: opposite direction
Energy: capacity to do work; SI unit = Joule (J)
Kinetic Energy (KE) = 0.5mv2; energy due to motion
Potential Energy (PE) = mgh; energy due to position/height
Law of Conservation of Energy: energy neither created nor destroyed, only transformed
In free fall: PE converts to KE; highest point max PE, ground max KE
Power = Work/Time = Energy/Time; SI unit = Watt (W); 1 HP = 746 W
1 kWh = 1 unit of electricity = 3.6 x 10^6 Joules
Forms of energy: mechanical, heat, light, sound, electrical, chemical, nuclear, solar
Energy conversions: Photosynthesis (solar to chemical), Generator (mechanical to electrical)
Work-Energy theorem: net work on object = change in kinetic energy
Efficiency = (useful output energy / total input energy) x 100%
Pendulum: continuous exchange between KE and PE; total mechanical energy constant
Elastic PE stored in compressed spring or stretched rubber band