1.1 energy changes in a system, and the ways energy is stored before & after such changes

what is work in physics?

work is done whenever energy is transferred from one store to another

what’s mechanical work?

work done when a force moves an object

what’s electrical work?

work done when a current transfers energy

give an example of mechanical work

a dog pulls a sledge: chemical energy (dog) → kinetic energy (sledge) → thermal energy (friction in sledge & ground)

equation for work done?

work done (j) = force (n) × distance (m)

what is kinetic energy?

energy stored in moving objects; stationary objects have 0 kinetic energy

equation for kinetic energy?

Ek = 0.5 × m × v²

what is elastic potential energy?

energy stored in a stretched spring; extension is proportional to force unless stretched beyond limit of proportionality

equation for elastic potential energy?

Ee = 0.5 × k × e²

what is gravitational potential energy?

energy stored due to an object’s position above earth’s surface

equation for gravitational potential energy?

Ep = m × g × h

what is thermal energy?

energy stored due to an object’s temperature

what is specific heat capacity?

energy required to raise 1 kg of a substance by 1 °c

equation for change in thermal energy?

ΔE = mass × specific heat capacity × temperature change

what is power?

the rate of energy transfer or work done; 1 watt = 1 j/s

equations for power?

power = energy transferred ÷ time or power = work done ÷ time