work, energy and power

define power

work done per unit time

define work done

when a force moves the point at which it acts in the direction of the force

what is the formula of work done

F s

why does direction matter when talking about work done

to be specific of where the point of application of a force is

what is positive work done

everything in one direction

what is negative work done

initial and final positions same direction, movement in opposite direction

what kind of quantity is work

scalar

what does work done on the force mean

negative work done

what does work done by the force mean

positive work done

when force and displacement are not in the same direction, how do you find the resultant

resolve the vectors

what do you need to remember with one joule and one newton

when a force of one newton moves its point of application by one metre in the direction of the force, one joule of work is done

unit for work done

joules

what is the typical value of energy rounded to the nearest order of magnitude?: radioactive decay of a nucleus

10^-13

what is the typical value of energy rounded to the nearest order of magnitude?: sound of speech on ear for 1 second

10^-8

what is the typical value of energy rounded to the nearest order of magnitude?: moonlight on face for 1 second

10^-3

what is the typical value of energy rounded to the nearest order of magnitude?: beat of the heart

1

what is the typical value of energy rounded to the nearest order of magnitude?: burning a match

10³

what is the typical value of energy rounded to the nearest order of magnitude?: large cream cake

10⁶

what is the typical value of energy rounded to the nearest order of magnitude?: energy released from 100kg of coal

10¹⁰

what is the typical value of energy rounded to the nearest order of magnitude?: earthquake

10¹⁹

what is the typical value of energy rounded to the nearest order of magnitude?: energy received on Earth from the sun in one year

10²⁵

what is the typical value of energy rounded to the nearest order of magnitude?: rotational energy of the Milky Way galaxy

10⁵⁰

what is the typical value of energy rounded to the nearest order of magnitude?: estimated energy of formation of the Universe

10⁷⁰

what does an object need to do work

energy

what quantity is energy

scalar

what unit is energy

joules

when an object, like a spring, is stretched, what does it store

energy to return to its original shape

what is the name of: energy due to position of a mass in a gravitational field

gravitational potential energy

what is the name of: energy due to motion

kinetic energy

what is the name of: energy stored due to stretching and compressing an object

elastic potential energy

what is the name of: energy due to the position of a charge in an electric field

electric potential energy

what is the name of: energy associated with waves in the electromagnetic spectrum

electromagnetic radiation

what is the name of: electromagnetic radiation from the Sun

solar energy

what is the name of: random kinetic energy and potential energy of the molecules in an object

internal energy

what is the name of: energy released due to chemical reactions

chemical reactions

what is the name of: energy transferred due to temperature difference

thermal/heat energy

formula for efficiency

useful energy output / total energy input

formula for power

work done / time taken

what is the value of power for: power to operate a small calculator

10^-6

what is the value of power for: light power from a torch

10^-3

what is the value of power for: loudspeaker output

10

what is the value of power for: manual labourer working continuously

100

what is the value of power for: water buffalo working continuously

10³

what is the value of power for: hair dryer

10³

what is the value of power for: motor car engine

10⁴

what is the value of power for: electric train

10⁶

what is the value of power for: electricity generating station output

10⁹

what is potential energy

ability for an object to do work as a result of its position or shape

what is gravitational potential energy

energy possessed by a mass due to its position in a gravitational field

what is the formula for change in gravitational potential energy

mass x acceleration by gravity x change in height

what is the formula of kinetic energy

½ x mass x velocity squared

how do you calculate the horizontal component with work done and distance moved

Force x cos() x displacement

Equation for: Gravitational potential energy

mass x acceleration of gravity x height

Equation for: electrical potential energy

electrical field strength x charge x displacement

Equation for: kinetic energy

(mass x velocity²) / 2

Equation for: thermal energy

mass x specific heat capacity x change of temperature

Equation for: elastic potential energy in a spring

(force x stretched length) / 2

Equation for: elastic potential energy in compressed gas

pressure x change in volume