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3 years ago

Two objects must be in contact for them to exert a force on each other. True False

Physics

1 answer:

Irina-Kira [14]3 years ago

5 0

Answer:

False

Explanation:

The given statement "Two objects must be in contact for them to exert a force on each other" is not true as there are many types of forces that doesn't require being in contact for exerting a force.

One such example is the gravitational force acting between two bodies. Gravitational force is the force of pull with which a body pulls another body without being in contact.

For two bodies of masses 'M' and 'm' separated at a distance of 'R', the gravitational force is given as:

$Force=\frac{GMm}{R^2}\\Where,G\to \textrm{Universal Gravitational constant}$

The gravitational force acts always act between bodies that have mass. The bodies are not in contact yet experience force.

Therefore, the given statement is false.

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Use the law of conservation of energy to explain why the work output of a machine can never exceed the work input

Veronika [31]

The law of conservation of energy states that energy is not created nor destroyed, rather it is only transferred or transmitted from one form to another. Now, the work exerted which is the input is only transformed to move the object which is now becomes the output work. Some are used to move the object, some are converted to other forms. That is why it is never greater than the input energy. Thank you for your question. Please don't hesitate to ask in Brainly your queries.

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3 years ago

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The spectrum of a distant star shows that one in 2 e6 of the atoms of a particular element is in its first excited state 7.5 eV

Alchen [17]

Answer:

The temperature of star is 5473.87 K

Explanation:

Given:

Energy difference $\Delta E = 7.5$ eV

The ratio of number of particle $\frac{N_{f} }{N_{i} } = \frac{1}{2 \times 10^{6} }$

Degeneracy ratio $\frac{g_{f} }{g_{i} } = 4$

From the formula of boltzmann distribution for population levels,

$\frac{N_{f} }{N_{i} } =\frac{g_{f} }{g_{i} } e^{-\frac{\Delta E}{kT} }$

Where $k =$ boltzmann constant = $8.62 \times 10^{-5} \frac{eV}{K}$

$\frac{1}{2 \times 10^{6} } =4 e^{-\frac{7.5 eV}{8.62 \times 10^{-5} T} }$

$8 \times 10^{6} } = e^{\frac{7.5 eV}{8.62 \times 10^{-5} T} }$

$\ln(8 \times 10^{6}) = {\frac{7.5 eV}{8.62 \times 10^{-5} T} }$

$T = {\frac{7.5 eV}{8.62 \times 10^{-5} \ln(8 \times 10^{6})} }$

$T = 5473.87$ K

Therefore, the temperature of star is 5473.87 K

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3 years ago

Which two energy sources can help a star maintain its internal thermal pressure? which two energy sources can help a star mainta

Lapatulllka [165]

Nuclear fusion and gravitational contraction

<span>constituent of star is hydrogen(including isotope) or helium. nuclear fission is almost impossible. D(deuterium; isotope of hydrogen) and T(tritium; also isotope of hydrogen) reacts and helium is formed. During this reaction, severe energy is generated. Heavier elements are formed and pulls each other. Gathered elements forms core of star. Gravity of the core prevents the gas to run away.</span>

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3 years ago

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Alex is standing still and throws a football with a speed of 10 m/s to his friend, who is also standing still. The two friends a

Phantasy [73]

The question is incomplete. It comes with a set of answer choices.

These are the answer choices:

Alex observes it as 10 m/s, and his friend observes it as less than 10 m/s.

Alex observes it as less than 10 m/s, and his friend observes it as 10 m/s.

Both Alex and his friend observe it as 10 m/s.

Both Alex and his friend observe it as less than 10 m/s.

Answer: Both Alex and his friend observe it as 10 m/s.

Justification:

1) The speed is relative to the frame of reference.

2) It is said that the both Alex and his friend are standing still.

3) Then, the speed they both see is the same, 10 m/s, respect the Earth (where they are standing still).

Of course, Alex is watching the ball moving away and his friend is seing it approaching, but it is not relevant for the question, as it deals with the speed which is only about magnitude, not direction.

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yanalaym [24]

Answer:

atoms bond together and forms molecules

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2 years ago

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