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GRADING CRITERIA WORK, ENERGY, POWER G-level: A work is done when an object moves a distance (in the direction of force). Work done= force x distance moved. The unit for work and energy is joule (J) or Nm. If an object is hauled (släpas) along a bed (underlag) , the force of friction (friktionskraften) tries to stop the movement. The greater friction , the greater the work to move an object a certain distance. The higher an object moves, the greater potential energy (lägesenergi) it gets. The greater speed and mass , the greater its kinetic energy (rörelseenergi). Potential energy can change to kinetic energy and vice versa. Energy is stored work. The law of conservation of energy (Energiprincipen): Energy can change from one type to another , but it cannot be made or destroyed. When energy is changed you always get heat energy . Levers (hävstänger) and inclined planes (lutande plan) are examples of machines. A machine is anything which makes forces more convenient to use. The golden rule of mechanics (Mekanikens gyllene regel) : What you gain in force, you loose in distance. The power (effect) is how much work is done during a certain time, usually 1 second. Power is measured in watts (W ; 1W=1Nm/s). Efficiency (verkningsgraden) is how much of the power input that becomes power output (hur stor del av den tillförda energin som lämnas I form av nyttig energi). It is usually given in %. VG-level: Calculate work , effect and efficiency. MVG-level: Advanced calculations of work, effect and efficiency.
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