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3 years ago

What’s the definition of friction

Physics

1 answer:

Snowcat [4.5K]3 years ago

7 0

Answer:

Friction is a force that rubs on a object which then causes something within that object to happen. There are many types of friction, though.

Explanation:

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What is the highest energy photon that can be absorbed by a ground-state hydrogen atom without causing ionization?

lakkis [162]

Highest energy photon absorbed: $2.18\cdot 10^{-18}J$

Explanation:

An atom is said to be (positively) ionised when it absorbs a photon, and as a consequence, an electron becomes energetic enough to escape the atom, leaving an excess of positive charge behind.

In order for the electron to escape, the energy of the absorbed photon must be exactly equal to the (negative) energy of the level in which the electron lies.

For an hydrogen atom, the energy levels are given by

$E_n = -13.6 \frac{1}{n^2}$

where this energy is measured in electronvolts, and n is the number of the energy level.

Since the energy is negative, this means that the electron which requires most energy is the one lying in the ground state (n=1). Therefore, for an electron in the ground state, the most energy that can be absorbed from the incoming photon is

$E_1 = -13.6 eV$

Converting into Joules, this is equal to

$E_1 = 13.6 \cdot 1.6\cdot 10^{-19}=2.18\cdot 10^{-18}J$

Learn more about hydrogen atom:

brainly.com/question/2757829

#LearnwithBrainly

3 0

3 years ago

For heat transfer purposes, an egg can be considered to be a 5.5-cm-diameter sphere having the properties of water. An egg that

Harrizon [31]

Answer:

The time taken is $t = 40007 sec$

Explanation:

From the question we are told that

The diameter of the egg is $d_e = 5.5cm = \frac{5.5}{100} = 5.5*10^{-2}m$

The initial temperature of egg the $T_e = 4.3^{o}C$

The temperature of the boiling water $T_b = 100^oC$

The heat transfer coefficient is $H = 800 W/m^2 \cdot K$

The final temperature is $T_e_f = 74^oC$

The thermal conductivity of water is $k = 0.607 W/m^oC$

The diffusivity of the egg $\alpha = 0.146 * 10^{-6} m^2 /s$

Using one term approximation

We have the

$\frac{T_e_f - T_b}{T_e - T_b} = Ae^{-\lambda ^2 \tau}$

The radius is $r = \frac{5.5*10^ {-2}}{2} =2.75*10^{-2}m$ Note that this radius is approximation to that of a real egg

Now we need to obtain the Biot number which help indicate the value of $A \ and \ \lambda$ to use in the above equation

The Biot number is mathematically represented as

$Bi = \frac{H r}{k}$

Substituting values

$Bi = \frac{800 * 2.75 *10^{-2}}{0.607}$

$= 36.24$

So for this value which greater than 0.1 the coefficient $\lambda_1 \ and \ A_1$ is

$\lambda = 3.06632$

$A = 1.9942$

Substituting this into equation 1 we have

$\frac{74- 100}{4.3 - 100} = 1.9942 e^{-(3.0632^2) \tau}$

$0.2717= 1.9942 e^{-(3.0632^2) \tau}$

$0.2717= 1.9942 e^{-9.383 \tau}$

$0.13624 = e^{-9.383 \tau}$

Taking natural log of both sides

$-1.993 = -9.383\ \tau$

$\tau = 0.2124$

The time required for the egg to be cooked is mathematically represented as

$t = \frac{\tau r^2}{\alpha }$

substituting value is

$= \frac{0.2124 * 2.75 *10^{-2}}{0.146 *10^{-6}}$

$t = 40007 sec$

8 0

3 years ago

Which of The following is the best example of water changing from a liquid to gas

expeople1 [14]

Answer:

There are no examples but this should be evaporation

Explanation:

4 0

3 years ago

A substance that does not react with metal, has a bitter taste, and turns litmus paper blue is a(n) ___.

Pavlova-9 [17]

The answer to the question is b because acid is a substance that tastes sour, reacts with metal and turns litmus paper blue

5 0

3 years ago

3. What is the main difference between a physical change and a chemical

Lana71 [14]

Answer:

B and D could both be right as they are quit similar.

Consider two rods of the same length and diameter,

Increasing the diameter of one would change the expansion qualities of that rod even though there would be no chemical changes,

However, leaving the physical appearance of both rods the same while applying a reactive substance (acid or something) to one of the rods would not necessarily change the physical appearance of that rod but could make a considerable change in the physical properties of that rod.

3 0

3 years ago