Answer:
The correct option is;
(c) 64W
Explanation:
Here we have the Coefficient Of Performance, COP given by
The heat change from 23° to 6°C for a mass of 10 kg/h which is equivalent to 10/(60×60) kg/s or 2.78 g/s we have
= m·c·ΔT = 2.78 × 4.18 × (23 - 6) = 197.39 J
Therefore, plugging in the value for in the COP equation we get;
which gives
Since we were working with mass flow rate then the power input is the same as the work done per second and the power input to the refrigerator = 63.674 J/s ≈ 64 W.
The power input to the refrigerator is approximately 64 W.
Answer:
Greenhouse gases keep our planet livable by holding onto some of Earth's heat energy so that it doesn't all escape into space. This heat trapping is known as the greenhouse effect. Just as too little greenhouse gas makes Earth too cold, too much greenhouse gas makes Earth too warm.
Answer:
(a) 
(b) 
(c) 1 s
(d) 20 m
(e) 1 m
(f) 
(g) 
(h) 
(i) 
(j) 
(k) 
(l) 
(m) 
Explanation:
Since <em>x</em> is measured in meters and <em>t</em> in seconds, constants <em>a </em>and <em>b</em> must have units that gives meters when multiplied by square and cubic seconds respectivly, so that would mean for <em>a </em>and for <em>b</em>.
We can get the velocity <em>v </em>equation by deriving the position with respect to <em>t</em>, which gives:
And the acceleration <em>a</em> equation by deriving again:
Now for getting the maximun position between 0 and 4, we must find to points where the positions first derivate is equal to cero and evaluate those points. That is <em>v=0</em>, which gives
For <em>t = 0</em>,<em> x = 0</em> so the maximun position is archieved at 1 second, which gives <em>x = 1 meter</em>.
For obtaining it's displacement <em>r</em>, we can integrate the velocity from 0 seconds to 4 seconds, which gives the mean value of the position in that interval:
For the remaining questions, we just replace the values of <em>t</em> on the respective equations.
A colloid I think. Don’t hold it against me if I’m wrong my dude.
Answer:
a. Temperatures increase can change a solid to a liquid, but cannot change a liquid to a solid
b. The particles in a solid are much closer together than the particles in a liquid.
Explanation:
Any material expands when heated and contracts when cooled. So, when a body is heated to a particular temperature, it starts melting and changes into a liquid.
As the material expands the distance between the atoms or molecules increases and it will become a liquid. So it can move around the material. It doesn't become solid on further heating. But water is an exception where it contracts when heated from 0° to 4° C.
In solids, these atoms or molecules are closely packed. It is rigidly fixed.
The solid, as well as the liquid, has a definite volume, but the liquid does not have a definite shape.
