Machines

Question 1

functions of simple machines

Answer 1

1. force multiplier
2. speed gainer
3. changing point of application of effort to a convenient point
4. changing direction of effort to a convenient direction

Question 2

define machine

Answer 2

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

Question 3

define load

Answer 3

a resistive or opposing force to be overcome by a machine

Question 4

define effort

Answer 4

a force applied on the machine to overcome the load

Question 5

define mechanical advantage

Answer 5

ratio of load to effort is called MA

Question 6

force multiplier

Answer 6

when MA is greater than 1
VR greater than 1

Question 7

speed gainer

Answer 7

when MA is lesser than 1
VR less than 1

Question 8

machine having MA equal to 1

Answer 8

change the direction of effort as there is no gain in force or speed

Question 9

define VR

Answer 9

ratio of velocity of effort to velocity of load is called VR
ratio of displacement of effort to displacement of load

Question 10

when VR equal 1

Answer 10

displacement of load is equal to displacement of effort. change in direction

Question 11

define work input

Answer 11

word done on the machine by effort

Question 12

define work output

Answer 12

work done by machine on the load

Question 13

define efficiency

Answer 13

ratio of the work done on the load by the machine to the work done on the machine by the effort

Question 14

define ideal machine

Answer 14

machine in which there is no loss in energy in any manner, work output = work input
efficiency= 100%

Question 15

loss of energy caused by

Answer 15

1. moving parts are not frictionless
2. string in it is not perfectly elastic
3. different parts are not perfectly rigid

Question 16

relationship between efficiency, MA, VR

Answer 16

MA of a machine is equal to the product of its efficiency and VR

Question 17

define lever

Answer 17

a rigid, straight/bent bar which is capable of turning about a fixed axis

Question 18

law of levers

Answer 18

the MA of a lever is equal to the ratio of the length of its effort arm to the length of its load arm

Question 19

three classes of levers

Answer 19

ELF: 3, 2, 1

Question 20

class 1 levers

Answer 20

MA and VR can have any value, either greater than, equal to, or less than 1

Question 21

class 2 levers

Answer 21

effort arm is always longer than load arm
MA and VR are always greater than 1
force multiplier

Question 22

class 3 levers

Answer 22

effort arm is always shorter than load arm
MA and VR always lesser than 1
speed gainer

Question 23

two pulleys

Answer 23

1. single fixed pulleys
2. movable pulley

Question 24

define single fixed pulley

Answer 24

a pulley which has its axis of rotation stationary in position

both load and effort act downwards , tension acts upwards
MA is less than 1
VR is equal to 1

Question 25

use of fixed pulley

Answer 25

to change the direction of the effort to be applied

Question 26

single movable pulley

Answer 26

a pulley whose axis of rotation is movable

load can be lifted by applying an effort equal to half the load, in ideal situation
force multiplier
MA is less than 2
VR is 2

Question 27

two ways of combination pulleys

Answer 27

1. using one fixed pulley and several movable pulleys attached to the same rigid support
2. using several pulleys in two blocks, when lower block is movable and upper block is fixed (block and tackle)

Question 28

MA and VR for combination pulleys

Answer 28

2 to the power of n movable pulleys with one fixed pulley

Question 29

effort required to balance a load in block and tackle system

Answer 29

load/ number of pulleys

Question 30

block and tackle acts as

Answer 30

force multiplier

Question 31

VR and MA of block and tackle

Answer 31

equal to the number of strands of the tackle