Work & Energy Lecture Notes

Flashcards about Work, Energy and Thermodynamics of the Human Body

Work

The way energy is transferred between one object/system and another.

Energy

Of central importance in all sciences; the total energy of an isolated system is conserved (constant).

Joule (J)

Unit for energy, work, and heat; equal to N m.

Work Done by a Constant Force

W = Fdcos(theta), where d is the distance moved and theta is the angle between F and d.

Physiological Work

Muscles under tension require energy to continually re-trigger muscle fibre contractions.

Efficiency (Muscles)

Ratio of useful output (physical work) to metabolic energy used, typically between 5-20%.

Kinetic Energy (KE)

KE = (1/2)mv^2, energy due to motion.

Work-Kinetic Energy Principle

Change of KE = W = work done on object when kinetic energy is the only energy that changes.

Gravitational Potential Energy (GPE)

GPE = mgy, energy an object has due to its height y.

Conservation of Energy

If an object falls freely due to gravity, gravitational potential energy decreases and kinetic energy increases, but the total energy (KE + GPE) remains constant.

Power

The time rate of transferring energy; measured in Watts (W) or J/s.