Work, energy, and power
Power
Forces
Internal
External
Work
Energy
Mechanical Energy
Potential Energy
Kinetic Energy
Energy transferred to/from an object by a force along a displacement
Key ingredients
Force
Displacement
Cause
Equation
W = F • d • cos Θ
Theta
The angle between any two plane
Negative work
When a force has a component opposite or against the displacement
Unit
Joule (J) = 1 Newton * 1 Meter
Stored energy of an object as the result of its position
Gravitational Potential Energy
Elastic Potential Energy
Energy stored in an object as the result of its vertical position or height
Energy stored in elastic materials as the result of their stretching or compressing
PEgrav = mass • g • height
Equations
Fspring = k • x
PEspring = 0.5 • k • x2
k = spring constant
x = amount of compression
(relative to equilibrium position)
Energy of motion
Types
Vibrational
Rotational
Translational
KE = 0.5 • m • v2
Energy possessed by an object due to its motion or position
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Can be either potential or kinetic
Ability to do work
Equations
TME = PE + KE
TME = PEgrav + PEspring + KE
The rate at which work is done
Equations
Unit
Watt = Joule/second
Power = Work / time=(Force*Displacement)/Time
Power = Force*(Displacement/Time)
Power=Force*Velocity
Applied force
Normal force
Tension force
Friction force
Air resistance force
Gravity forces
Magnetic force
Electrical force
Spring force
Positive work
The object gains energy
The object loses energy