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3 years ago

99 POINTS

Physics

1 answer:

antoniya [11.8K]3 years ago

8 0

Answer:

Send a pic of it so i can mark it.

Explanation:

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A giant log float on a lake while a tiny grain of sand sinks to the bathroom. Explain why a heavy object like the log floats whi

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Answer:

Because the log is hollow or is less dense

Explanation:

If a log has little density, it will float. While sand is dense and completely solid, so it will sink.

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If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then

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Answer:

b. the planets are marble-size or smaller and the nearest stars are thousands of miles away

Explanation:

The correct answer for the question is option b because if the distance between sun and Pluto is any scale is made equivalent to a walking distance of some minutes then the size of planets will be equivalent to the size of marbles and the nearest stars that is present in Alpha centauri triple star system(4.5 light years away) will be approximately thousands of miles away from us.

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3 years ago

A 63-kg hiker is climbing the 828-m-tall Burj Khalifa in Dubai. If the efficiency of converting the energy content of the bars i

konstantin123 [22]

Answer:

$T_f=5854.76$ °C

Explanation:

Given:

mass of hiker, m= 63 kg

height to be climbed, h= 828 m

energy produced by an energy bar, $E= 1.10\times 10^6 J$

heat capacity of the hiker, $c=75.3 J.mol^{-1}.K^{-1}= 4.184 J.kg^{-1}.K^{-1}$

initial body temperature of hiker, $T_i=36.6 \degree C$

<em>The efficiency of converting the energy content of the bars into the work of climbing is 25%, the remaining 75% of the energy released through metabolism is heat released to her body.</em>

We find the energy required for climbing 828 m height:

W=m.g.h

$W=63\times 9.8\times 828$

W= 511207.2 J

∵Hike eats 2 energy bars= $2\times 1.1\times 10^{6} J$

Energy produced $= 2.2\times 10^{6} J$

Now, according to her efficiency:

Total energy required for producing the work of W= 511207.2 J which is required to climb the given height will be (say, E):

$25\% of E= 511207.2$

$\Rightarrow E= 511207.2\times \frac{100}{25}$

$E=2044828.8 J$

Amount of total energy (E) converted into heat(Q) is:

$Q=2044828.8-511207.2\\Q=1533621.6J$

As we know that:

heat, $Q=m.c. (T_f-T_i)$ .................(1)

where:

$T_f$ is the final temperature

Putting respective values in the eq. (1)

$1533621.6= 63\times 4.184\times (T_f-36.6)$

$(T_f-36.6)\approx 5818.16$

$T_f\approx 5854.76$ °C

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3 years ago

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It is B. false that an instrument used to detect a static electric charge is called an ammeter. It is actually called an electroscope. Ammeter measures current.

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Brainlest would be much appreciated.

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