Answer:
\frac{dh}{dt}_{h=2cm} =\frac{40}{9\pi}\frac{cm}{2}
Explanation:
Hello,
The suitable differential equation for this case is:

As we're looking for the change in height with respect to the time, we need a relationship to achieve such as:

Of course,
.
Now, since the volume of a cone is
and the ratio
or
, the volume becomes:

We proceed to its differentiation:

Then, we compute 

Finally, at h=2:

Best regards.
Answer:
1) The power needed to process 50 ton/hr is 135.4 HP.
2) The void fraction of the bed is 0.37.
Explanation:
1) For this type of milling operations, we can estimate the power needed for an operation according to the work index (Ei), the passing size of the circuit feed (F80) and the passing size of the product (P80).
We assume the units of Ei are kWh/t.
The equation that relates this parameters and the power is (size of particles in μm):

The power needed to process 50 ton/hor is

2) The density of the packed bed can be expressed as

being f the fraction and ρ the density of every fraction. We know that the density of the void is 0 (ρv=0) and that fv=1-fs (the sum of the fractions ois equal to the total space).
Then we can rearrange

The void fraction of the bed is 0.37.
Answer:
In water hydrogen bonding formed between partially negative oxygen and partially positive hydrogen atoms.
Explanation:
Hydrogen bond is a partially electrostatic attraction between hydrogen (H), which is bonded to a more electronegative atom such as nitrogen (N), oxygen (O) or fluorine (F), and another adjacent atom bearing a lone pair of electrons.
In water molecule hydrogen and oxygen have difference in electronegativity, due to which dipoles are form. One is partial positive on hydrogen atom and other is partial negative on oxygen atom. The electrostatic attraction occur between two oppositely charged poles which is known as hydrogen bonding.
Animals are able to see much more clearly in the dark than humans can.
Or
Humans are able to see much more clearly in the dark than animals can.
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