Answer:



Explanation:
Given:
- Length of block,

- Breadth of block,

- height of block,

- Thermal conductivity of the block,

- Temperature on the hotter side,

- temperature on the cooler side,

- time for which the heat flows,

<u>REFER THE ATTACHED IMAGE FOR THE REFERENCE</u>
<em>The rate of heat flow using </em><em>Fourier's law</em><em> of conduction is given as:</em>

<u>Now the amount heat flow perpendicular to the pink surface:</u>


<u>Now the amount heat flow perpendicular to the orange surface:</u>


<u>Now the amount heat flow perpendicular to the green surface:</u>


The two different isotopes have weights :
w1 = 78.918 amu
w2 = 80.916 amu
average weight w3 = 79.903 amu
The mixing of two components can be modeled as
let the fraction of w1 be 'x'
hence 
now this is a linear equation in 'x'. Substituting the values we get
x = 0.507
hence the percentage of Br79 = 50.7% and the percentage of BR81 = 49.3%
Answer:

Explanation:
The formula for linear expansivity, 
original length, l₁ = 123 cm = 1.23 m
final length, l₁ = 92.6 cm =0.926 m
original temperature, θ₁ = 200°C
Linear expansivity, α = 2 * 10⁻⁵ °C⁻¹
Putting these values into the formula:

Answer:
8
Explanation:
Applying,
v = λf................ Equation 1
Where v = velocity/ speed of the wave, λ = wave length of the wave, f = number of waves the person surf in one seconds.
make f the subject of the equation
f = v/λ............ Equation 2
From the question,
Given: v = 1.6 m/s, λ = 24 m
Substitute these values into equation 2
f = 1.6/24
f = 0.0667 wave/seconds.
If,
in one seconds, the person surf a total wave crest of 0.0667
Therefore,
in one hours, he will surf a total wave crest of (0.0667×60×60) = 240 waves crest
He rides for every 30th wave crest,
Hence,
number of wave crest the person surf in one hour = 240/30 = 8