Energy, Work, & Power

• Energy = capacity to do work (joules or kcal)

• Work = change in energy of a system (joules)

  • work= ∆energy= energy_final-energy_initial

• Power= rate at which work is performed (watts= joules/sec)

Energy in human movement

• Kinetic energy (KE = 1/2mv²)

  • associated w/ motion

  • depends on mass and velocity, no mass = no KE

• Potential Energy

  • stored energy

  • mechanical: PE_gravity or PE_elastic

  • PE_gravity = mg∆h

  • PE_elastic=1/2k∆x²

    • k= “stiffness”

    • ∆x = change in object length

  • PE_chemical=transfer of energy from one bond in a molecule to another bond in ATP

Work