energy changes in systems

chemical energy

fuels, foods, chemicals in batteries

transferred during chemical reactions

kinetic energy

energy an object has bcs its moving

gravitational potential energy

energy stored in an object bcs of its position eg. ground

elastic potential energy

energy stored in a springy object when squashed or stretched

thermal energy

describes the energy a substance has bcs of its temperature

kinetic energy = (0.5 × mass × speed^2)

E(k) = 1/2  m v^2

elastic potential energy = 0.5 × spring constant × (extension)^2

E(e) = 1/2  k e^2

gravitational potential energy =

mass × gravitational field strength × height

E(p) = m g h

change in thermal energy =

mass × specific heat capacity × temperature change

∆ E  = m c  ∆ θ

system

object or group of objects

energy , e (m)

joules , J

mass , m (m)

kilograms , kg

speed , v (m)

metres per second , m/s

spring constant , k (m)

newtons per metre , n/m

extension , e (m)

metres, m

gravitational field strength, g (m)

newtons per kilogram, n/kg

power (def)

the rate at which energy is stored or work is done

power = energy transferred / time

or

power = work done / time

P =E / t

P = W / t

power , P (m)

watts , W

time , t (m)

seconds , s

work done , W (m)

joules , J

1 joule, 1J p/s =

= 1 watt , 1W

energy can be transferred usefully, stored, or dissipated but __

__ cannot be created or destroyed