4. Which of the following statement is correct
The density of an object does not remains same if we take small quantity of that substance.
The density of an object remains same irrespective of its shape, size and quantity.
The density of an object does not remains same irrespective of its shape and size.
The density of an object remains same only if its shape and size remains same.

Anybody wanna ? (picture included? )

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.

In a good thermo flask the main cause of heat loss is