Work, Energy and Power Flashcards
Energy,
definition
key idea
a calculated quantity that is conserved during any change, that which is transferred when a force does work
Work is done on a body when a force moves the body in the direction of the force, energy is transferred from one body to another
Work done formula,
in words
in symbols x 2
key idea
work done = force x distance
W = F x s
W = Fs {cos or sin} θ
work done = energy transferred
Joule definition,
in words
formula
the work done when a force of one newton moves a distance of 1 metre in the direction of the force
1 joule = 1 newton x 1 metre
1J = 1Nm
Gravitational potential energy definiton
the energy a body has done due to its position in a gravitational field
Gravitational potential energy formula,
in words
in symbols
change in gpe = weight x change in height
∆Ep = mg∆h
Kinetic energy formula,
in words
in symbols
kinetic energy = half mass x speed squared
Ek = 1/2 • m • v^2
Efficiency formula
efficiency =
(useful output energy / total input energy) • 100
Principle of conservation of energy definition
energy cannot be created or destroyed, it can only be changed from one form to another
Power definition
the power of a device is the rate at which it does work per unit time
Power formula,
in words x 2
in symbols x 2
power = work done / time taken power = force x velocity
P = W / t P = F x v
Watt definition
one watt is one joule per second
