Topic 1 (Energy)

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Types of Energy

Energy can be created or destroyed. It can only be transferred from one store to another.

Kinetic (movement) energy store - objects are moving or speeding up

Gravitational energy store - objects are raised up and can glide

Elastic energy store - objects are squeezed or streched

Thermal energy store - objects are warmer or hotter

Chemical energy store - chemicals react such as fuel

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Energy equations

Work Done - Force x Distance Moved

KInetic Energy - 1/2 x mass x velocity2

Gravitational potential energy - mass x gravity x height

Elastic potential energy - 1/2 x spring constant x extension2

GPE - MASS X CHANGE IN HEIGHT X GRAVITATIONAL FIELD STRENGTH

w= FS

Work is the amount of energy transferred.

Mechanical work is the force(push and pull) are used to move and object meaning work is done.

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Practise Questions

1) The change in gravitational potential energy is 500 J, the height of the bar is mass= 80 kg

2) Fred pushes a lawn mower 20 metres and apllies a 15 N force what work is Fred doing?

3) What is the work done if we apply a 7 N force and we move 8 metres in the direction of the force?

4) What force is required to move 7 M if the work done is 21 J?

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1)  800= 80 x 10  800 ÷ (80 x10) = 1m  Gpe = 800 J   Kinetic energy is 400 J

2) 20 x 15  = 300 J

UNITs

Distance units = metres (M)

Work done units = Joules (J)

Force units = Newtons (N)

Store energy = energy transferred

GPE= Gravitational potential energy

M / S = Metres per second

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Energy efficency

Energy Efficeny =   useful output energy (J)

total input energy (J)

Specific heat capacity = amount of energy needed to raise the temperature of 1 kg of material by 1 degrees

unit = J/kg degrees

E = MCO   E= energy transferred (J)  M = mass (kg)   C = specific heat capacity (J/kg degrees)

O = change in temperature.

E ÷ (M x C) / block O

= E ÷ (M x O) / block C

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