Machines

Question 1

Force multiplier means

Answer 1

by lifting a heavy body by applying less amount of effort

Question 2

rear wheel of cycle is an example of ______.

Answer 2

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

Question 3

lifting bucket from the well is an example of

Answer 3

changing direction of effort to a convenient direction

Question 4

machines also work as obtaining ______ in speed

Answer 4

gain , greater movement of load by less movement effort

Question 5

gain in speed formula -

Answer 5

gain in speed = 1/ velocity ratio

Question 6

define machine -

Answer 6

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

Question 6

Load means

Answer 6

a resistive or opposing force to be overcome by a machine

Question 6

effort means

Answer 6

force applied on a machine to overcome a load

Question 6

mechanical advantage -

Answer 6

ratio of load and effort

Question 7

mechanical advantage - formula

Answer 7

load / effort

Question 8

when the mechanical advantage be less than 1

Answer 8

when the effort is greater than load

Question 9

when mechanical advantage is greater than 1

Answer 9

when effort is less than load

Question 10

when the M.A is 1

Answer 10

when effort = load

Question 11

if mechanical advantage is more than 1 the machine acts as

Answer 11

force multiplier

Question 12

if a machine as M.A less than 1

Answer 12

it acts as gain in speed

Question 13

if m.a = 1

Answer 13

it generally acts to change the direction of effort

Question 14

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

Answer 14

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

Question 15

velocity ratio means

Answer 15

ratio of velocity of effort/ load

Question 16

velocity ratio [as displacement ]

Answer 16

ratio of displacement of E/ displacement of L

Question 17

when is velocity ratio be less than 1

Answer 17

displacement of load is more than displacement of effort

Question 18

when velocity ratio is less than 1 it called as

Answer 18

gain in speed

Question 19

when is velocity ratio is more than 1

Answer 19

when displacement of load is less than displacement of effort

Question 20

when velocity ratio is more than 1 machine acts as

Answer 20

force multiplier

Question 21

velocity ratio = 1 if ?

Answer 21

displacement of load = displacement of effort ,

Question 22

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

Answer 22

change in direction of effort

Question 23

work input means

Answer 23

work done on the machine by effort

Question 24

work output

Answer 24

work done by the machine on the load

Question 25

efficiency means

Answer 25

ratio of work output / work input

Question 26

efficiency denoted by

Answer 26

η [eta]

Question 27

when mechanical advantage decreases

Answer 27

due to friction and weight of the parts

Question 28

if mechanical advantage decreases _________ decreases

Answer 28

efficiency

Question 29

load point means

Answer 29

the point were the energy is obtained by overcome the load

Question 30

effort point

Answer 30

point at which energy is supplied to machine by applying effort

Question 31

input energy

Answer 31

work done at the effort point

Question 32

output energy

Answer 32

work obtained at the load point

Question 33

no machine has efficiency _________

Answer 33

greater than 1 [ more than 100%]

Question 34

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

Answer 34

it will violate law of conservation of energy

Question 35

what is ideal machine ?

Answer 35

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

Question 36

in ideal machine work output is = _____

Answer 36

work input

Question 37

in ideal machine efficiency is _____

Answer 37

100%

Question 38

what is mean by actual machine ?

Answer 38

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

Question 39

how loss of energy happens in machine [ actual ]

Answer 39

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

Question 40

in actual machine most prominent loss of energy is due to

Answer 40

friction , energy loss by heat

Question 41

how will a machine heated

Answer 41

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

Question 42

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

Answer 42

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

Question 43

formula for work output -

Answer 43

load * displacement of load

Question 44

work input - [formula]

Answer 44

effort * displacement of effort

Question 45

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

Answer 45

m.a / v.r

Question 46

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

Answer 46

equal

Question 47

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

Answer 47

LESS

Question 48

two types of single pully -

Answer 48

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

Question 49

single fixed pully means

Answer 49

pully which as its axis of rotation stationary

Question 50

what happens if tension throughout the string is not same ?

Answer 50

string will move even when the pully is not moving

Question 51

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

Answer 51

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

Question 52

IN ACTUAL PRATICE M.A advantage is _____ in pully

Answer 52

less than 1

Question 53

why is fixed pully used ?

Answer 53

to only change the direction of effort applied

Question 54

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

Answer 54

always 1

Question 55

Single movable pully means

Answer 55

pully whose axis of rotation is movable

Question 56

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

Answer 56

2

Question 57

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

Answer 57

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

Question 58

in actual single movable pully efficiency is

Answer 58

less than 100%

Question 59

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

Answer 59

as we need to give more amount of effort than load

Question 60

what mean by block ?

Answer 60

a frame which as two or more pully is block

Question 61

the string passing over the pulleys in block

Answer 61

tackle

Question 62

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

Answer 62

fixed

Question 63

block and tackle system the lower frame as ______type of pulley

Answer 63

movable

Question 64

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

Answer 64

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

Question 65

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

Answer 65

load / number of pulley's

Question 65

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

Answer 65

load / number of pulley's

Question 66

m.a in terms of inclusive of weight

Answer 66

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

Question 67

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

Answer 67

light