Chapter 6 - Work, Energy and Power Flashcards
Define “energy”
The capacity to do work
What is the SI unit for energy?
joule (J)
Energy is a ________ (scalar/vector) quantity
scalar
What are some forms of non-potential energy?
kinetic energy, light energy, sound energy, electrical energy, thermal energy, nuclear energy
What are some forms of potential energy?
gravitational potential energy, elastic potential energy, chemical potential energy, magnetic potential energy
Energy can be ________ from one form to another
converted
Define “kinetic energy”
The energy a body possesses due to its motion
Formula to calculate kinetic energy
K.E. = 1/2mv^2
[ kinetic energy = 1/2 x mass x velocity ]
Define “gravitational potential energy”
The energy a body possesses because of its position relative to the ground
Formula to calculate gravitational potential energy
G.P.E. = mgh
[ gravitational potential energy = mass x height x gravitational field strength ]
State the principle of conservation of energy
Energy cannot be created or destroyed, but only changes from one form to another
The total amount of energy in the universe is ________
always the same
Define “work done”
The amount of energy that has been converted from one form to another or transferred from one body to another
What is the SI unit for work?
joule (J)
Work is a ________ (scalar/vector) quantity
scalar
Formula to calculate work done
W = F x d
[ work done = force x distance moved in the direction of the force ]
Define “power”
The rate of doing work
or: the rate at which energy changes of one form to another
Formula to calculate power
Power = W/t = ΔE/t
[ power = work done/time taken = energy change/time taken ]
What is the SI unit for power?
watt (W)
1 W = 1 ____
J s^-1
Define “efficiency”
The ratio of the useful energy output to the total energy input
Efficiency is usually expressed as ________
a percentage
Formula to calculate efficiency
Efficiency = (useful energy output/total energy input) x 100%
Since useful energy output ________ than the total energy input, the efficiency of a system ________
cannot be greater
cannot be greater than 100%
