A spherical shell of outer radius R and inner radius R/2 contains a solid sphere of radius R/2 (see figure). The density of the material of the solid sphere is ρ and that of the shell is ρ/2. What is the average mass density of the larger sphere thus formed?
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3ρ/4
9ρ/16
7ρ/8
5ρ/8
The human eye is like a camera that has a lens with :
fixed focal length and fixed aperture size.
variable focal length and fixed aperture size.
fixed focal length and variable aperture size.
variable focal length and variable aperture size.
The relative atomic mass of boron (which exists in two isotopic forms 10B and 11B) is 10.81. What will be the abundance of 10B and 11B, respectively (consider a sample of 100 atoms)?
19% and 81%
81% and 19%
38% and 62%
62% and 38%
Which among the following are essential constituents of Portland cement?
Sand, lime, clay
Silica, alumina, lime
Silica, lime, graphite powder
Sand, graphene, clay