work, energy and power

texbook references: Mike Crundell, Geoff Goodwin - Cambridge International AS & A Level Physics student's book 3rd edition |||

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 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: electrical potential energy

electrical field strength x charge x displacement

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

what is gravitational potential energy

energy due to position of a mass in a gravitational field

what is kinetic energy

energy due to motion

what is elastic potential energy

energy stored due to stretching or compressing an object

what is electric potential energy

energy due to the position of a charge in an electric field

what is electromagnetic radiation

energy associated with waves in the electromagnetic spectrum

what is solar energy

electromagnetic radiation from the sun

what is internal energy

random kinetic and potential energy of the molecules in an object

what is chemical energy

energy released during chemical reactions

what is thermal energy

energy transferred due t otemperature difference

what change to an object can make it store the ability to do work

changing shape. moving vertical or horizontal position

what is the law of conservation of energy

energy cannot be created or destroyed. it can only be converted from one for to another

if energy dissipates from an object, what happens to the energy in the atmosphere/universe

stays constant at all times

why can the efficiency of an object never exceed 100%

energy cannot be created

how can efficiency be written

as a ratio or percentage

what is the unit for power

watt

what is another formual for power that isn’t work done / time taken

force x velocity

what is newton’s law of gravitation

all masses attract one another

if we pull away from the surface of the earth, what do we gain

gravitational potential energy

what is translational kinetic energy

energy of an object moving in a straight line

what is rotational kinetic energy

energy of rotating objects

what happens to an object when dropped in terms of GPE and KE

loses GPE and gains KE

what happens when you throw an object up in terms of GPE and KE

gains GPE and loses KE

how much is 1 N m in joules

1 J

what is 1 Watt

1 joules per second

how come when you hold weight up you feel like you are doing a lot of work but physics says you are not doing any work

work is done only when a force moves

what does the area of a force displacement graph five you

work done

what does the gradient of a force displacement graph give you

rate at which the applied force changed per unit displacement

what does a positive gradient in a force displacement graph mean

force increases with displacement

what does a negative gradient in a force displacement graph mean

force decreases with displacement

what does a constant gradient in a force displacement graph mean

linear relation with force and displacement

what does zero gradient on a force displacement graph mean

constant force applied

if you are working out power with work done and time taken and the work rate is not steady, what will the equation of power work out

average power

what kind of quantity is power

scalar

what do we mean when we say energy is dissipated

trasferred to the surroundings

what is the most likely reason for apparent energy loss in a system

friction

what is a machine

any device that transfers energy from one form to another

what happens to energy in a system when it is transferred in terms all efficiency

not all fo it is transferred in a useful way

what is proportion of energy that is usefully transferred

efficiency

what is this?

Sankey diagram

what does a sankey diagram help with

visualisation of where energy goes in a system

why can momentum and kinetic energy link

both depend on mass and velocity

what is kinetic energy with momentum

momentum² / 2m

if you double momentum, what happens to kinetic energy

kinetic energy increases by 4x

what is an elastic collision in regard of kinetic energ y

kinetic energy is conserved

what is inelastic collision regarding kinetic energy

kinetic energy is greater before the collision and less after collision