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3 years ago

What happens to the sound of a train whistle as a train approaches and passes you? why?

1 answer:

8 0

This is called, The Doppler effect.

In short terms, when the trains is farther away the wavelength of the whistles sound are longer and more separate from each other, and more farther away from you, as it gets closer to you, the wavelengths start getting shorter and more louder the closer it gets to you. Basically the wavelengths change because of the motion of the source.

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Correctly round the following number to the whole number 2.35784

Elina [12.6K]

Answer:2

Explanation:

8 0

3 years ago

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

You sit "at rest" in front of your computer to answer this question. But you sit on the surface of a planet that spins, so even

igomit [66]

Answer: Linear speed is 1,670 Kph.

Explanation:

If we assume that the earth is a perfect sphere, and that is spinning itself once every roughly 24 hr, we can get the angular velocity of the Earth, in magnitude, as follows:

ω = 2π / 24 Hr

Now, by definition, an angle is the relationship between the arc s, and the radius r, so we can replace these values in the angular velocity expression, as follows:

ω = (Δs / r) . 1/Δt ⇒ ω = (Δs/Δt). 1/r

But, by definition, Δs/At, is just the linear velocity, v, so we can conclude the following;

ω = v/r ⇒ v = ω. r

So, we can get v, as follows:

v = 2π /24 hr . 6378 Km = 1,670 Km/hr.

4 0

3 years ago

A ball is suspended by a lightweight string, as shown in the figure above.

Irina18 [472]

Answer

A. 1 and 2

Explanation

At point 1 we have the highest potential energy and the kinetic energy is zero.

At 2 the potential energy is minimum and the kinetic energy is maximum.

The law of conservation of energy says that energy cannot be created nor destroyed. So, the change in P.E = Change in K.E.

P.E = height × gravity × mass. The height referred here is the perpendicular height. Gravity and mass are constant in this case.

From the diagram it can be seen clearly that the vertical height from 2 to 1 is much greater than from 4 to 3.

This shows that the change in P.E is greater between 1 and 2 and so is kinetic energy.

6 0

3 years ago

Read 2 more answers

May you help me answer this

Firdavs [7]

1) See three Kepler laws below

2a) Acceleration is $2.2 m/s^2$

2b) Tension in the string: 27.4 N

3a) Kinetic energy is the energy of motion, potential energy is the energy due to the position

3b) The kinetic energy of the object is 2.25 J

Explanation:

There are three Kepler's law of planetary motion:

1st law: the planets orbit the sun in elliptical orbits, with the Sun located at one of the 2 focii
2nd law: a segment connecting the Sun with each planet sweeps out equal areas in equal time intervals. A direct consequence of this is that, when a planet is further from the sun, it travels slower, and when it is closer to the sun, it travels faster
3rd law: the square of the period of revolution of a planet around the sun is directly proportional to the cube of the semi-major axis of its orbit. Mathematically, $T^2 \propto r^3$ , where T is the period of revolution and r is the semi-major axis of the orbit

2a)

To solve the problem, we have to write the equation of motions for each block along the direction parallel to the incline.

For the block on the right, we have:

$M g sin \theta - T = Ma$ (1)

where

$Mg sin \theta$ is the component of the weight of the block parallel to the incline, with

M = 8.0 kg (mass of the block)

$g=9.8 m/s^2$ (acceleration of gravity)

$\theta=35^{\circ}$

T = tension in the string

a = acceleration of the block

For the block on the left, we have similarly

$T-mg sin \theta = ma$ (2)

where

m = 3.5 kg (mass of the block)

$\theta=35^{\circ}$

From (2) we get

$T=mg sin \theta + ma$

Substituting into (1),

$M g sin \theta - mg sin \theta - ma = Ma$

Solving for a,

$a=\frac{M-m}{M+m}g sin \theta=\frac{8.0-3.5}{8.0+3.5}(9.8)(sin 35^{\circ})=2.2 m/s^2$

2b)

The tension in the string can be calculated using the equation

$T=mg sin \theta + ma$

where

m = 3.5 kg (mass of lighter block)

$g=9.8 m/s^2$

$\theta=35^{\circ}$

$a=2.2 m/s^2$ (acceleration found in part 2)

Substituting,

$T=(3.5)(9.8)(sin 35^{\circ}) +(3.5)(2.2)=27.4 N$

3a)

The kinetic energy of an object is the energy due to its motion. It is calculated as

$K=\frac{1}{2}mv^2$

where

m is the mass of the object

v is its speed

The potential energy is the energy possessed by an object due to its position in a gravitational field. For an object near the Earth's surface, it is given by

$U=mgh$