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ioda
3 years ago
8

The freezer compartment in a conventional refrigerator can be modeled as a rectangular cavity 0.3 m high and 0.25 m wide with a

depth of 0.5 m. Determine the thickness of styrofoam insulation (k = 0.30 W/m⋅K) needed to limit the heat loss to 400 W if the inner and outer surface temperatures are −10 and 33°C, respectively.
Physics
1 answer:
Mkey [24]3 years ago
3 0

Answer:

Thickness of Styrofoam insulation is 0.02741 m.

Explanation:

Given that,

Height = 0.25 m

Depth = 0.5 m

Power = 400 W

Temperature = 33°C

We need to calculate the area of Styrofoam

Using formula of area

A=2(lb+bh+hl)

Put the value into the formula

A=2(0.3\times0.5+0.25\times0.5+0.5\times0.3)

A=0.85\ m^2

Inner surface temperature of freezer

T_{i}=-10°C=263\ K

Outer surface temperature of freezer

T_{o}=33+273=306\ K

We need to calculate the thickness of Styrofoam insulation

Using Fourier law,

q=\dfrac{kA}{L}(T_{o}-T_{i})

L=\dfrac{kA}{q}(T_{o}-T_{i})

Put the value into the formula

L=\dfrac{0.30\times0.85}{400}(306-263)

L=0.02741\ m

Hence, Thickness of Styrofoam insulation is 0.02741 m.

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cestrela7 [59]

Answer:

13.37 rev/min

Explanation:

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r = 9 m

Centripetal acceleration (a_c) is given by:

a_c=\frac{v^2}{r} \\\\v=\sqrt{a_c*r} \\\\v=\sqrt{17.64\ m/s^2*9\ m}\\\\v=12.6\ m/s

The velocity (v) is given by:

v = ωr;  where ω is the angular velocity

Hence:

ω = v/r = 12.6 / 9

ω = 1.4 rad/s

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4 0
2 years ago
Consider dropping a ball from rest. This ball moves from astate of high gravitational potential energy to one of lowgravitationa
Leni [432]

Answer:

From the negative to the positive cable.

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3 0
3 years ago
If the torque required to loosen a nut that holds a wheel on a car has a magnitude of 55 n·m, what force must be exerted at the
erastova [34]

Either 175 N or 157 N depending upon how the value of 48° was measured from.    
You didn't mention if the angle of 48° is from the lug wrench itself, or if it's from the normal to the lug wrench. So I'll solve for both cases and you'll need to select the desired answer.    
Since we need a torque of 55 N·m to loosen the nut and our lug wrench is 0.47 m long, that means that we need 55 N·m / 0.47 m = 117 N of usefully applied force in order to loosen the nut. This figure will be used for both possible angles.    
Ideally, the force will have a 0° degree difference from the normal and 100% of the force will be usefully applied. Any value greater than 0° will have the exerted force reduced by the cosine of the angle from the normal. Hence the term "cosine loss".     
If the angle of 48° is from the normal to the lug wrench, the usefully applied power will be:  
U = F*cos(48)  
where  
U = Useful force  
F = Force applied    
So solving for F and calculating gives:  
U = F*cos(48)  
U/cos(48) = F  
117 N/0.669130606 = F  
174.8537563 N = F    
So 175 Newtons of force is required in this situation.    
If the 48° is from the lug wrench itself, that means that the force is 90° - 48° = 42° from the normal. So doing the calculation again (this time from where we started plugging in values) we get  
U/cos(42) = F  
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6 0
2 years ago
. If you live in a region that has a particular TV station, you can sometimes pick up some of its audio portion on your FM radio
Reil [10]

Answer:

Please see below as the answer is self-explanatory.

Explanation:

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6 0
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julia-pushkina [17]

There's not enough information to find an answer.

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