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ki77a [65]
3 years ago
8

One end of an insulated metal rod is maintained at 100 ∘C and the other end is maintained at 0.00 ∘C by an ice–water mixture. Th

e rod has a length of 70.0 cm and a cross-sectional area of 1.10 cm2 . The heat conducted by the rod melts a mass of 8.70 g of ice in a time of 15.0 min .
find the thermal conductivity k of the metal?
k=............ W/(m.K)
Physics
1 answer:
lozanna [386]3 years ago
8 0

Answer:

k=105.0359\times 10^4\,W.m^{-1}.K^{-1}

Explanation:

Given:

temperature at the hotter end, T_H=100^{\circ}C

temperature at the cooler end, T_C=0^{\circ}C

length of rod through which the heat travels, dx=0.7\,m

cross-sectional area of rod, A=1.1\times 10^{-4}\,cm^2

mass of ice melted at zero degree Celsius, m=8.7\times 10^{-3}\,kg

time taken for the melting of ice, t=15\times60=900\,s

thermal conductivity k=?

By Fourier's Law of conduction we have:

\dot{Q}=k.A.\frac{dT}{dx}......................................(1)

where:

\dot{Q}=rate of heat transfer

dT= temperature difference across the length dx

Now, we need the total heat transfer according to the condition:

we know the latent heat of fusion of ice,  L = 334000\,J.kg^{-1}

Q=m.L

Q=8.7\times 10^{-3}\times 334000

Q=2905.8\,J

Now the heat rate:

\dot{Q}=\frac{Q}{t}

\dot{Q}=\frac{2905.8}{900}

\dot{Q}=3.2287\,W

Now using eq,(1)

3.2287=k\times 1.1\times 10^{-4} \times \frac{100}{0.7}

k=205.4606\,W.m^{-1}.K^{-1}

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The correct answer is letter C. Volume is decreasing. For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume<span> are </span>inversely proportional<span>. </span>
3 0
3 years ago
Two 4.0 kg masses are 1.0 m apart on a frictionless table. Each has 1.0 μC of charge.What is the magnitude of the electric force
xeze [42]

Coulomb's law:

  Force = (<span>8.99×10⁹ N m² / C²<span>) · (charge₁) · (charge₂) / distance²

            = (</span></span><span>8.99×10⁹ N m² / C²<span>) (1 x 10⁻⁶ C) (1 x 10⁻⁶ C)  / (1.0 m)²

            = (8.99×10⁹ x 1×10⁻¹² / 1.0)  N

            =      8.99×10⁻³  N

            =        0.00899 N repelling.

Notice that there's a lot of information in the question that you don't need.
It's only there to distract you, confuse you, and see whether you know
what to ignore.

-- '4.0 kg masses';  don't need it. 
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-- 'frictionless table';  don't need it.
   Friction has no effect on the force between them,
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7 0
3 years ago
If two equal charges are separated by a certain distance, the force of repulsion is F. Given F1, if each charge in F1 is doubled
Alisiya [41]

Answer:F_2=16\times F_1

Explanation:

Given

Force of repulsion between two charge particle is given by force F

Electrostatic force is given by

F=\frac{kq_1q_2}{r^2}

where q_1 and q_2 is the charges  of particle

r=distance between charge particle

=\frac{kq^2}{r^2}when charges are doubled and distance is reduced to half

i.e. q become 2 q and r becomes 0.5 r

F_2=\frac{k(2q)^2}{(0.5r)^2}

F_2=\frac{kq^2}{r^2}\times 4\times 4

F_2=16\times F_1

         

6 0
3 years ago
A pendulum has a mass of 1.5 kg and starts at a height of 0.4 m. If it is released from rest, how fast is it going when it reach
ella [17]

Answer:

A. 2.8 m/s

Explanation:

Suppose that at the height of 0 m, the path of the pendulum is lowest.

If we use law of conservation of energy, the pendulum will have zero kinetic energy or K.E when it is at highest point, because K.E happens during movement of object and at the highest point all the energy will be P.E

                                                    P.E= mgh

Similarly, when the pendulum reaches at the lowest point, the height becomes zero and the P.E also becomes zero. Now all the energy will be K.E

                                               K.E= 1/2 m v^2

In question, we are asked about the speed as the pendulum  it reaches the lowest point of its path. Like we mentioned P.E will be zero at lowest point  because of zero height. And also we will use law of conservation of energy because no energy has been lost from system.

                                                  K.E=     P.E

                                       1/2 m v^2  =   mgh

Taking sq.root at both sides

                                                  v= Under root 2 gh

                                                   v=Under root 2x 9.8 m/s x0.4 m

                                                   v=Under root 7.84

                                                    v=2.8 m/sec

Hope it helps!

3 0
3 years ago
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motikmotik

Answer: Gravity

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4 0
2 years ago
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