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3 years ago

Sodium has a work function of 2.46 eV.

Physics

1 answer:

bazaltina [42]3 years ago

5 0

Answer:

Explanation:

given, work function of Φ = 2.46 eV.

converting the eV to joule, we have

2.45 * 1.6*10^-19 J

The cutoff wavelength is the wavelength where the incoming light does not have enough energy to free an electron, i.e. all of

the photon’s energy will be channeled into trying overcoming the work function barrier.

It is mathematically given as

Φ = hf

f = Φ/h

f = (2.46 * 1.6*10^-19) / 6.63*10^-34

f = 3.936*10^-19 / 6.63*10^-34

f = 5.94*10^14 Hz as our cut off frequency

λf = c,

λ = c/f

λ = 3*10^8 / 5.94*10^14

λ = 5.05*10^-7

λ = 505 nm as our cut off wavelength

K(max) = hf - Φ

K(max) = hc/λ - Φ

K(max) = [(6.63*10^-34 * 3*10^8) / 181*10^-9] - 3.936*10^-19

K(max) = (1.989*10^-25/181*10^-9) - 3.936*10^-19

K(max) = 1.1*10^-18 - 3.936*10^-19

K(max) = 7.064*10^-19 J or 4.415 eV

V(s) = K(max) / e

V(s) = 4.612 V

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A flywheel in a motor is spinning at 510 rpm when a power failure suddenly occurs. The flywheel has mass 40.0 kg and diameter 75

8_murik_8 [283]

Complete Question

A flywheel in a motor is spinning at 510 rpm when a power failure suddenly occurs. The flywheel has mass 40.0 kg and diameter 75.0 cm . The power is off for 40.0 s , and during this time the flywheel slows down uniformly due to friction in its axle bearings. During the time the power is off, the flywheel makes 210 complete revolutions. At what rate is the flywheel spinning when the power comes back on(in rpm)? How long after the beginning of the power failure would it have taken the flywheel to stop if the power had not come back on, and how many revolutions would the wheel have made during this time?

Answer:

$\theta=274rev$

Explanation:

From the question we are told that:

Angular velocity $\omega=510rpm$

Mass $m=40.kg$

Diameter d $75=>0.75m$

Off Time $t=40.0s$

Oscillation at Power off $N=210$

Generally the equation for Angular displacement is mathematically given by

$\theta_{\infty}=\frac{w+w_0}{t}t$

$w=\frac{2*\theta_{\infty}}{t}-w_0$

$w=\frac{28210}{40*(\frac{1}{60})}-510$

$w=120rpm$

Generally the equation for Time to come to rest is mathematically given by

$t=(\frac{\omega_0}{\omega_0-\omega})t$

$t=(\frac{510}{510-120rpm})(40.0)(\frac{1}{60})$

$t=0.87min$

Therefore Angular displacement is

$\theta =(\frac{120+510}{2})0.87$

$\theta=274rev$

6 0

3 years ago

Which of the statements concerning light are true? The speed of light is the same no matter what material it is traveling throug

wel

Answer:

The statements that are true concerning light are the last three statements:

Its propagation direction is perpendicular to both the electric field and the magnetic field.

It moves at a constant speed through a vacuum.

The speed of light in matter is less than the speed of light in a vacuum.

Explanation:

Light is electromagnetic waves.

The properties of the electromagnetic waves were established by James Clerk Maxwell.

They included that they are the result of the oscillation of a magnetic field in phase with an electric field which are always is always perpendicular to each other.

Also, the electromagnetic waves propagate at right-angles to the direction of both the magnetic and the electric field, meaning that they are a type of transverse wave.

Thus, the second statement ("Its propagation direction is parallel to both the electric field and the magnetic field") is false, and the fourth statement ("Its propagation direction is perpendicular to both the electric field and the magnetic field") is true.

On the other hand, it is a postulate of the special theory of relativity that the speed of light is a constant (absolute value) in vacuum: nothing can travel faster than what light travels in vacuum. Thus, the fifth statement, "It moves at a constant speed through a vacuum" is true.

About the speed of light in matter, it is always less than the speed of light in vacuum. Thus, the first statement, "the speed of light is the same no matter what material it is traveling through", and the third statement "the speed of light in matter is greater than the speed of light in a vacuum" are false; while the last statement, "the speed of light in matter is less than the speed of light in a vacuum" is true.

The explanation on why the speed of light is less in a medium than in vacuum is related with the fact that at nanoscopic level the waves suffer polarization which means deviations from the straighi path, which makes that the net straight propagation is slower.

8 0

4 years ago

A car traveling in a straight line has a velocity of 6m/s at some instant. After 6.32s its velocity is 13.2m/s . What is the ave

NeX [460]

Average acceleration = (change in speed) / (time for the change) .

Average acceleration = (13.2 - 6) / (6.32) = 7.2 / 6.32 = about 1.139... m/s² .

8 0

3 years ago

Consider an e. coli to be a cylinder with a diameter of 1 micrometer (um) and with a length of 2 micrometer (um).

julia-pushkina [17]

Answer:

$A=6.28\ \mu m^2$

Part 1

$V=1.57 \ \mu m^3$

Part 2

$A=6.28\ \mu m^2$

Explanation:

Given that

Diameter,d=1 μm

Length ,l=2 μm

As we know that volume of cylinder given as

$V=\pi r^2l$

$V=\pi \times 0.5^2\times 2 \ \mu m^3$

$V=1.57 \ \mu m^3$

Surface area,A

A=π d l

$A=\pi \times 1 \times 2\ \mu m^2$

$A=6.28\ \mu m^2$

Part 1

$V=1.57 \ \mu m^3$

Part 2

$A=6.28\ \mu m^2$

4 0

4 years ago

Suppose that you are standing on a train accelerating at 0.39g. What minimum coefficient of static friction must exist between y

timurjin [86]

Answer:

0.39

Explanation:

In order not to slide, you must have exactly the same acceleration of the train:

$a=0.39 g$

where

g = 9.81 m/s^2

There is only one force acting on you: the static frictional force that "pulls" you forward, and it is given by

$F_s = \mu_s mg$

According to Newton's second law, the net force acting on you (so, the frictional force) must be equal to your mass times the acceleration, so we have

$F= ma = \mu_s mg$

from which we find

$\mu_s = \frac{a}{g}=\frac{0.39 g}{g}=0.39$

so, the minimum coefficient of static friction must be 0.39.

5 0

3 years ago