Topic 1 (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

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.

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?

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

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