Asked by sayeedafatima250 | 9th Apr, 2021, 10:12: AM

Expert Answer:

Let n be number of pulleys , T be tension in the cord and f is total friction force in the system ,
then we have
 
L + f = n T = n E
 
where E is effort which is equal to Tension T
 
Hence , number of pulleys n =  ( L + f ) / E .............. (1)
 
Let us assume acceleration due to gravity g = 10 m/s2 .
 
friction force f = 300 N = 300 /10 = 30 kgf
 
Hence number of pulleys n is determined from eqn.(1)
 
n = ( 120 + 30 ) / 25  = 6
 
Mechanical advantage MA = ( L / E ) = [ ( n E ) - f ] / E = n - ( f / E ) = 6 - ( 30/25) = 4.8
 
Velocity ratio VR = number of pulleys = n
 
Efficiency =  ( MA ) / ( VR ) = 4.8 /6 = 0.8

Answered by Thiyagarajan K | 9th Apr, 2021, 04:22: PM