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Work Energy Power > Machines > Flashcards

Machines Flashcards

1
Q

Force multiplier means

A

by lifting a heavy body by applying less amount of effort

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2
Q

rear wheel of cycle is an example of ______.

A

changing the point of application of effort to a convenient point .

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3
Q

lifting bucket from the well is an example of

A

changing direction of effort to a convenient direction

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4
Q

machines also work as obtaining ______ in speed

A

gain , greater movement of load by less movement effort

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5
Q

gain in speed formula -

A

gain in speed = 1/ velocity ratio

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6
Q

define machine -

A

machine is a device by which we can overcome a large resistive force by applying less effort at convenient point and desired direction or by which we can obtain gain in speed

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6
Q

Load means

A

a resistive or opposing force to be overcome by a machine

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6
Q

effort means

A

force applied on a machine to overcome a load

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6
Q

mechanical advantage -

A

ratio of load and effort

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7
Q

mechanical advantage - formula

A

load / effort

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8
Q

when the mechanical advantage be less than 1

A

when the effort is greater than load

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9
Q

when mechanical advantage is greater than 1

A

when effort is less than load

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10
Q

when the M.A is 1

A

when effort = load

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11
Q

if mechanical advantage is more than 1 the machine acts as

A

force multiplier

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12
Q

if a machine as M.A less than 1

A

it acts as gain in speed

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13
Q

if m.a = 1

A

it generally acts to change the direction of effort

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14
Q

machine can’t be used as force multiplier as well as speed multiplier [simultaneously ] why?

A

in force multiplier - effort < load , in speed multiplier - effort > load

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15
Q

velocity ratio means

A

ratio of velocity of effort/ load

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16
Q

velocity ratio [as displacement ]

A

ratio of displacement of E/ displacement of L

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17
Q

when is velocity ratio be less than 1

A

displacement of load is more than displacement of effort

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18
Q

when velocity ratio is less than 1 it called as

A

gain in speed

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19
Q

when is velocity ratio is more than 1

A

when displacement of load is less than displacement of effort

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20
Q

when velocity ratio is more than 1 machine acts as

A

force multiplier

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21
Q

velocity ratio = 1 if ?

A

displacement of load = displacement of effort ,

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22
Q

if a machine as velocity ratio = 1 such machines generally does

A

change in direction of effort

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23
Q

work input means

A

work done on the machine by effort

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24
Q

work output

A

work done by the machine on the load

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25
Q

efficiency means

A

ratio of work output / work input

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26
Q

efficiency denoted by

A

η [eta]

27
Q

when mechanical advantage decreases

A

due to friction and weight of the parts

28
Q

if mechanical advantage decreases _________ decreases

A

efficiency

29
Q

load point means

A

the point were the energy is obtained by overcome the load

30
Q

effort point

A

point at which energy is supplied to machine by applying effort

31
Q

input energy

A

work done at the effort point

32
Q

output energy

A

work obtained at the load point

33
Q

no machine has efficiency _________

A

greater than 1 [ more than 100%]

34
Q

output energy can never be greater than input energy why ?!

A

it will violate law of conservation of energy

35
Q

what is ideal machine ?

A

a machine in which there is no loss of energy [ no dissipation of energy in undesired form ]

36
Q

in ideal machine work output is = _____

A

work input

37
Q

in ideal machine efficiency is _____

A

100%

38
Q

what is mean by actual machine ?

A

machine which has loss of energy , work output is not equal to work input

39
Q

how loss of energy happens in machine [ actual ]

A

due to weight of parts and friction , string is not perfectly elastic , different parts are non rigid

40
Q

in actual machine most prominent loss of energy is due to

A

friction , energy loss by heat

41
Q

how will a machine heated

A

some energy’s will lost as heat which heats the moving parts of machine

42
Q

if efficiency of machine is 80% what does it means ?

A

80% energy is obtained as useful energy , 20% lost in overcoming friction

43
Q

formula for work output -

A

load * displacement of load

44
Q

work input - [formula]

A

effort * displacement of effort

45
Q

Efficiency = [in terms of M.A and V.R ]

A

m.a / v.r

46
Q

in ideal Machine - M.a is _____ to v.r

A

equal

47
Q

in actual machine - M.A is _________ to V.R

A

LESS

48
Q

two types of single pully -

A

by fixing the axis [ fixed position ] , by changing it axis of rotation [ movable pully ]

49
Q

single fixed pully means

A

pully which as its axis of rotation stationary

50
Q

what happens if tension throughout the string is not same ?

A

string will move even when the pully is not moving

51
Q

in case of neglecting the friction and mass of string - the m.a , v.r and efficiency of the single fixed pully is

A

M.A = 1 , V.R = 1 , EFFICIENCY = 100%

52
Q

IN ACTUAL PRATICE M.A advantage is _____ in pully

A

less than 1

53
Q

why is fixed pully used ?

A

to only change the direction of effort applied

54
Q

for gain in speed velocity ratio must be less than 1 but for single fixed pully velocity ratio is ________.

A

always 1

55
Q

Single movable pully means

A

pully whose axis of rotation is movable

56
Q

in neglecting the weight of pully and friction , M.A and V.R is equal to

A

2

57
Q

in actual single movable pully - M.A and V.R IS -

A

m.a less than 2 and v.r remains 2

58
Q

in actual single movable pully efficiency is

A

less than 100%

59
Q

why in actual single movable pully the M.A is less than 2

A

as we need to give more amount of effort than load

60
Q

what mean by block ?

A

a frame which as two or more pully is block

61
Q

the string passing over the pulleys in block

A

tackle

62
Q

in block and tackle system the upper frame as _______ type of pulley

A

fixed

63
Q

block and tackle system the lower frame as ______type of pulley

A

movable

64
Q

pulley’s in lower block is [ number of pulley’s ]

A

equal to or less than 1 [number of pully’s ]

65
Q

effort = __________ [ load and number of pulley’s]

A

load / number of pulley’s

65
Q

effort = __________ [ load and number of pulley’s]

A

load / number of pulley’s

66
Q

m.a in terms of inclusive of weight

A

m.a = n-w/e , number of pulley -n , w - total weight of lower block

67
Q

for greater efficiency in block and tackle system , lower block should be _______

A

light

Work Energy Power (5 decks)

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