Chapter 5: Work, Energy and Power Flashcards
when is work done?
when energy is transferred
what is the equation for work done?
W = Fx
work done = force x displacement
what are some assumptions made with W = Fx
- Force is a fixed value in any calculations, constant or average force
- Equations assume that the direction of the force is in the same direction and along the same line of movement
- Equation gives the definition of a Joule: “One Joule is the work done when a force if 1N moves through a distance of 1m”
Whats the equation of work done when the force is not in the direction of motion?
W = Fx cosθ
what is the equation for power and velocity?
power = force x velocity
what is the equation of kinetic energy?
0.5 x m x v2
what is the equation for GPE?
mgh
what is the equation for efficiency?
useful energy output
——————————- x 100
total energy input
what is the equation of energy transfer for falling objecs?
mgh = 0.5 x m x v2
what is the principle of conservation of energy?
total energy of a closed system remains constant as energy cannot be created or destroyed, but can be transferred
Define Work done?
The product of the magnitude of a force and the distance moved by the object in the direction of the force
Unit: Joules
Define Kinetic Energy and give its SI base units
KE: energy associated with the motion of an object with mass
SI base units: kg m2s-2
Define Gravitational Potential Energy
energy of an object due to its position in a gravitational field
Define Elastic Potential Energy
energy stored by an object as a result of a reversible change in its shape
what is the rate of work done equal to?
power
