a cylinder of mass 10g weights 7g in water.if the area of crosssection is 0.75square its length will be..
 
 
 

Asked by ujjwalviky2003 | 2nd Nov, 2017, 07:13: PM

Expert Answer:

area of crosssection is given as "0.75 square". we assume it is 0.75 square cm. 
wiht this assumption the answer is given below
 
As per law of floatation , weight of solid when it is fully immersed in water is given by
 
begin mathsize 12px style V open parentheses rho subscript s minus rho subscript w close parentheses g space equals space w e i g h t space m e a s u r e d space i n space w a t e r end style
V is volume, ρ is density( s for solid, w for water).

begin mathsize 12px style T h e space B o y a n c y space f o r c e space i s space V rho subscript w g space equals space V rho subscript s g space minus space left parenthesis W e i g h t space M e a s u r e d space i n space w a t e r right parenthesis

V rho subscript w g space equals space left parenthesis 10 space minus space 7 right parenthesis g
space sin c e space V rho subscript s g space w e i g h t space m e a s u r e d space i n space a i r space g i v e n space a s space 10 g

sin c e space rho subscript w space equals space 1 space comma space w e space g e t space V o l u m e space a s space 3 space c m cubed
end style
When volume is divided by crosssection, we can get length.
 
If that is done we can get the length as 4 cm

Answered by  | 13th Dec, 2017, 07:34: PM