A uniform metre scale is balanced at 60 cm mark,when weights of 5 gf and 40 gf are suspendedat 10cm and 80 cm mark respectively.Weight of the metre rule will be 

a) 45 gf

b)55 gf

c) 65 gf

d)None

Asked by soojaataa | 14th Jul, 2020, 11:56: AM

Expert Answer:

 
L e t space W space b e space t h e space w e i g h t space o f space t h e space m e t r e space s c a l e space w h i c h space a c t s space a t space t h e space m i d p o i n t space o f space r u l e r space w h i c h space i s space 50 space c m space
C l o c k space w i s e space m o m e n t space space equals space 40 space cross times left parenthesis 80 space minus 60 right parenthesis space equals space 40 space cross times 20 space equals 800 space g f minus c m
A n t i c l o c k w i s e space m o m e n t space equals space 5 cross times left parenthesis 60 minus 10 right parenthesis space plus thin space W space cross times space left parenthesis 60 minus 50 right parenthesis space equals space 250 space plus space 10 space W space
B y space p r i n c i p l e space o f space m o m e n t comma space
A n t i c l o c w i s e space m o m e n t space equals space C l o c k space w i s e space m o m e n t space
T h u s comma space
800 space equals space 250 space plus space 10 space W
800 space minus space 250 space equals space 10 space W space space
W space space equals space 55 space g f space 
Hence , the weight of metre rule is 55 gf 

Answered by Shiwani Sawant | 14th Jul, 2020, 08:40: PM