Answer:

Explanation:
If
-
,
are temperatures of gasses and liquid in Kelvins,
and
are thicknesses of gas layer and steel slab in meters,
,
are convection coefficients gas and liquid in
,
is the contact resistance in
,
- and
are thermal conductivities of gas and steel in
,
then: part(a):

using known values:
part(b): Using the rate equation :
the surface temperature 
and 
Similarly


The temperature distribution is shown in the attached image
Answer: Option (c) is the correct answer.
Explanation:
Physical properties are the properties in which there is no change in chemical composition of a substance. On the other hand, chemical properties are the properties which change the chemical composition of a substance.
For example, when water boils at
then it changes into vapor state whereas when water freezes at
then it changes state from liquid to solid.
This means only physical state of water is changing and there is no change in chemical composition of water.
Hence, we can conclude that best option describing given information is that these are the physical changes water undergoes.
Answer:d
Explanation:
Spring is compressed to a distance of x from its equilibrium position
Work done by block on the spring is equal to change in elastic potential energy
i.e. Work done by block 
therefore spring will also done an equal opposite amount of work on the block in the absence of external force
Thus work done by spring on the block 
Thus option d is correct
Answer:
Decreased by a factor of 4.5
Explanation:
"We have Newton formula for attraction force between 2 objects with mass and a distance between them:

where
is the gravitational constant on Earth.
are the masses of the object and Earth itself. and R distance between, or the Earth radius.
So when R is tripled and mass is doubled, we have the following ratio of the new gravity over the old ones:




Since
and 

So gravity would have been decreased by a factor of 4.5
Answer:
3100 m/s
Explanation:
The relationship between frequency and wavelength of a wave is given by the wave equation:

where
v is the speed of the wave
f is its frequency
is the wavelength
For the wave in this problem,
f = 15,500 Hz

Therefore, the wave speed is
