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3 years ago

15 POINTS PLEASE PLEASE HELP ME!!

Physics

1 answer:

abruzzese [7]3 years ago

3 0

I will not help you but i would surely take these points for answering this question but i lied.

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What happens when fusion begins in the outer shell of a star? The energy produced causes the star to contract into a dwarf. The

Aleks [24]

Answer:

Explanation:

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2 years ago

What is meant by global warming?

pychu [463]

The global warming is the uniform heating of the globe due to the effect of greenhouse gases.

Answer: Option B

<u>Explanation:</u>

Global warming is thus the theory that says that earth is warming up with an increase in temperature over time due to increment in the greenhouse gases.

These are greenhouse gases that are getting increased due to the human activity or say over exploitation of the natural resources. The heating of the globe has caused ozone layer depletion which is also causing warming.

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3 years ago

A piston-cylinder device contains Helium gas initially at 150 kPa, 20 o C, and 0.5m 3 . The helium is now compressed in a polytr

Molodets [167]

Answer:

Explanation:

Given

$P_1=150 kPa$

$T_1=20^{\circ}C$

$V_1=0.5 m^3$

$T_2=140^{\circ}C$

$P_2=400 kPa$

R for Helium $R=2.076$

$c_v=3.115 kJ/kg-K$

mass of gas $m=\frac{P_1V_1}{RT_1}$

$m=\frac{150\times 0.5}{2.076\times 293}$

$m=0.123 kg$

Similarly $V_2$ can be found

$\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}$

$V_2=0.264 m^3$

Work done $W=\int_{V_1}^{V_2}PdV$

$W=\frac{P_2V_2-P_1V_1}{n-1}$

$W=\frac{mR(T_2_T_1)}{n-1}$

Since it is a polytropic Process

therefore $PV^n=c$

$P_1V_1^n=P_2V_2^n$

$(\frac{V_1}{V_2})^n=\frac{P_2}{P_1}$

$(\frac{0.5}{0.264})^n=\frac{400}{150}$

$n=\frac{\ln 2.66}{\ln 1.893}$

$n=1.533$

$W=\frac{0.123\times 2.076(140-20)}{1.533-1}$

$W=57.48 kJ$

From Energy balance

$E_{in}-E_{out}=\Delta E_{system}$

Neglecting kinetic and Potential Energy change

$Q_{in}+W_{in}=change\ in\ Internal\ Energy$

Change in Internal Energy $\Delta U=u_2-u_1$

$\Delta U=mc_v(T_2-T_1)$

$\Delta U=0.123\times 3.115(140-20)$

$\Delta U=45.977 kJ$

$Q_{in}+57.48=45.977$

$Q_{in}=-11.50 kJ$

i.e. Heat is being removed

3 0

3 years ago

Standard weight and scales in the market should be checked in every two year why?

disa [49]

Answer:

to check for errors.

Explanation:

since some of the components of the scale are metallic, they are prone to rusting which would cause error in reading of the scale so there is organized checking if the scale to correct that.

hope it helps .

7 0

3 years ago

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Kenneth ran a marathon (26.2 miles) in 5.5 hours. What was Kenneth's average speed? (Round your answer to the nearest tenth.) 0.

Anna11 [10]

Answer:

4.8 mph

Explanation:

From the question,

Average speed = total distance/total time

V = d/t....................... Equation 1

Where d = distance, t = time

Given: d = 26.2 miles, t = 5.5 hours.

Substitute these values into equation 1

V = 26.2/5.5

V = 4.76 mph

V ≈ 4.8 mph

5 0

3 years ago

Read 2 more answers