P1- Conervation and dissipation of energy

P1

• Energy - stored in different energy stores 

• transferred by heating, waves , electric current , a force when it moves an object. 

• When an onject falls and gains speed its gravitational potentiall difference energy store decreases and its kinetic energy store increases.

• when a falling object hits the floor without bouncing, its kinetic energy store is transfered by heating to the thermal energy store of the object and surroundings. Sound waves move away from point of impact. 

• Energy - cant be created or destroyed!

• Conservation of energy applies to all energy changes. 

• A Closed System = an isolated system where NO energy transfers take place in or out of the the system. 

• Energy can be transferred between energy stores within a closed system. 

• Work done is when a force makes an object move. 

• Energy transferred = work done. 

• Work done = Force x distance 

• Increases when object moves up.                                    

• decreases when object moves down.                                       

• Increases when lifted up as work is done. 

• Gravitational field strength on Earth = 9.8N/kg

• The GFS on the moon is 1/6 less than earths.

• on a moving object kinetic energy store depends on its mass and speed. 

• kinetic energy store ;  E =  1/2 M X V^2 

• elastic potential energy = energy stored in an elastic when work is done 

• elastic potential energy in a stretched elastic; E = 1/2 k x e^2    
• e = extention of spring ^^^^^^

• Useful energy is good! It goes to the place we want it too go to! 

• Wasted energy is NOT GOOD! Its transferred by an undesired pathway. 

• wasted enrgy is then transferred to surrondings, making it warmer. 

• As energy dissipates (spreads) it gets less useful!! cries ;(

• Effeciency = useful energy transferred by device/ total energy supplied to device (x 100%)

• no energy transfer can be more than 100% efficient. Cries ;(

• machines waste energy because of friction between their moving parts, air resistance,electrical resisitance and noise. 

• machines can be more efficient by reducing waste engergy. 

• Electricity, gas and oil = most used in a home. 

• can transfer energy in the form of useful energy at the flick of a switch! Yayya!!

• everyday appliences usage = heating, lighting, making objects move and producing sound and visual images. 

• electrical applience is designed for a a particualar purpose and should waste as little energy as possible...

• power is a rate of transfer of energy

• power of applience; P = E/T

• Effiecincy = useful power out / total power in (x 100)

• power wasted = total power input - useful power output.