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timofeeve [1]
2 years ago
13

A charged cell phone has chemical energy stored in its battery. As you use your phone, the amount of chemical energy in the batt

ery decreases. Why is this not a violation of the first law of thermodynamics?
Physics
1 answer:
Lunna [17]2 years ago
6 0

Answer:

Because the chemical energy is converted to electrical enegy in the cell phone

Explanation:

This set up is not a voilation of the first law of thermodynamics because the chemical energy is not lost, it is only being transformed into electrical energy.

According to the first law of thermodynamics "energy is neither created nor destroyed but transformed from one form to another".

  • In a charged cell phone, the chemical energy is being transformed to electrical energy as you use it.
  • A phone cannot directly be powered with chemical energy.
  • The energy transformation to electrical energy makes it possible to use the phone.
  • In this process no energy is lost nor created. But simply, energy is transformed.
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Workers do 8000 J of work on a 2000-N crate to push it up a ramp. If the ramp is 2 m high, what is the efficiency of the ramp?
IRISSAK [1]

Answer:

50%

Explanation:

Efficiency = work out / work in

e = Fd / W

e = (2000 N) (2 m) / (8000 J)

e = 0.5

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2 years ago
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Study the free body diagram above. Which scenario below can best be described with this free body diagram? A. a cup is at rest o
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Answer: D

Explanation:

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4.A photon of green light strikes an unknown metal and an electron is emitted. The voltage is set to 2 volts. The electron canno
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4) The correct answer is:
<span>B. An electron will be emitted in the second experiment, but it cannot be determined whether it will reach the second plate. 

In fact, violet light has higher frequency than green light. This means that photons of violet light carry more energy than photons of green light (remember that the energy of a photon is proportional to its frequency: </span>E=hf)<span>, so when they hit the surface of the metal, more energy is transferred to the electrons. The electron was already emitted with green light, so it must be emitted also with violet light, given the more energy transferred. The electron will also have more kinetic energy when hit by violet light, however, we cannot determine if it will reach the second plate, since we don't know how much energy has been used to extract the electron from the metal (in fact, we don't know the work function of the metal, i.e. the energy needed to extract the electron)


3)  The correct answer is
</span><span>A. Violet light will cause electrons to be emitted at greater velocities than those removed by green light.

In fact, </span>violet light has higher frequency than green light. This means that photons of violet light carry more energy than photons of green light (remember that the energy of a photon is proportional to its frequency: E=hf), so when they hit the surface of the metal, more energy is transferred to the electrons. Therefore, the emitted electrons will have on average greater energy (and so, greater velocity) than those removed by green light.
3 0
2 years ago
The gas tank of Dave’s car has a capacity of 12 gallons. The tank was 38 full before Dave filled it to capacity. It cost him $2.
m_a_m_a [10]

Answer:

$ 18.75            

Explanation:

given,                                              

capacity of the Dave’s car = 12 gallons

Assuming that the tank is 3/8 full before

Cost of gas per gallon =  $2.50 per gallon of gas

Volume Dave have to fill                      

       =1 - \dfrac{3}{8}                          

       =\dfrac{5}{8} of full tank              

       =\dfrac{5}{8}\times 12              

volume Dave have to fill = 7.5 gallons          

total money Dave spent                  

     = 7.5 gallons x $2.50                

     = $ 18.75                                            

Dave have to spend $ 18.75 to fill tank to it capacity.

5 0
2 years ago
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The electric field produced by a large flat plate with uniform charge density on its surface can be found by using Gauss law, and it is equal to
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where
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We see that the intensity of the electric field does not depend on the distance from the plate. Therefore, the strenght of the electric field at 4 cm from the plate is equal to the strength of the electric field at 2 cm from the plate:
E=30 N/C
7 0
2 years ago
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