Work, Energy and Power

Reaction Rocket

Work A force is said to do work if, when acting, there is a displacement of the point of application in the direction of the force. https://en.wikipedia.org/wiki/Work_(physics) Measure of energy transfer that occurs when an object is moved over a distance by an external force at least part of which is applied in the direction of the displacement. https://www.britannica.com/science/work-physics

Work (Constant F)

Dot Product

Linear Work (F constant) W = F Dr cosq F q r

Linear Work (F not constant)

Work by a non-constant force Work is the area under the F vs. x curve

Work = change in mechanical energy Work Energy Theorem W = DE Work = change in mechanical energy

The sum of the potential and kinetic energies Mechanical Energy The sum of the potential and kinetic energies U = potential energy K = kinetic energy E = U + K

Conservative Force A force is conservative if: The work done between point A and B is independent of the path The work done around any closed path is zero

Non-Conservative Force Friction

Conservation of Mechanical Energy If the only work done on an object is by a conservative force, then the mechanical energy of the object is conserved.

Conservation of Energy The total energy of an isolated system is conserved. The energy can be transferred from one object to another or transformed from one form to another, but energy cannot be created or destroyed.

Potential Energy

Work Done By Gravity h mg

Gravitational Potential Energy

Hooke’s Law x

Work Done By A Spring

Elastic Potential Energy

Work by Net Force v2 = 20 m/s v1 = 10 m/s

Kinetic Energy

Net Work = change in kinetic energy Work Energy Theorem, Pt. 2 Wnet = DK Net Work = change in kinetic energy

Power

Power (alternate equation)

Energy Diagram A diagram that displays energy as a function of displacement Normally used to display potential energy

General Form Unstable Equilibrium Neutral Equilibrium

Circular Motion