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ollegr [7]
3 years ago
8

Lithium was one of the metals studied by the American physicist Robert Millikan in his research on the photoelectric effect. Whe

n illuminated with blue light of frequency 6.64 x 10" Hz, the photoelectrons ejected from a lithium surface have a maximum kinetic energy of 0.332 eV. What is the threshold frequency for lithium? For this problem, let the value of Planck's constant, h, be 6.63 x 10J's
Physics
1 answer:
faltersainse [42]3 years ago
4 0

Answer:

 f = 7.9487 10¹³ Hz

Explanation:

The photoelectric effect was correctly explained by Einstein assuming that the radiation is composed of photons, which behave like particles.

           hf = K + Ф

It indicates the frequency and the kinetic energy, let's look for the work function

          Ф = hf - K

let's reduce the magnitudes to the SI system

          K = 0.332 eV (1.6 10⁻¹⁹ J / 1 eV) = 0.5312 10⁻⁻¹⁹ J

let's calculate

          Ф = 6.63 10⁻⁻³⁴  6.64 10¹¹ - 0.5312 10⁻¹⁹

          Ф = 4.40 10⁻²² - 0.5312 10⁻¹⁹

          Ф = 5.27 10⁻²⁰ J

for the minimum frequency that produces photoelectrons, the kinetic energy is zero

           hf = Ф  

           f = Ф / h

           f = 5.27 10⁻²⁰ / 6.63 10⁻³⁴

           f = 7.9487 10¹³ Hz

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Answer:

5. Is greater than mg, always

Explanation:

If the cone has an inclination of angle β, the sum of forces will be:

x-axis (centripetal axis):

N*sin β = m*ax  where ax is the centripetal acceleration

y-axis:

N*cos β - m*g = m*ay   where ay is the vertical acceleration. If the block starts falling down, ay will be negative. If the block starts sliding up, ay will be positive. If the block does not move up nor down, ay=0.

Solving for N:

N = \frac{m*g + m*ay}{cos \beta }

If ay is positive or zero, N will be greater than mg. If ay is negative, N will be less than mg.

If the block is sliding along a horizontal circular path (not up, nor down), ay = 0, so N will always be greater than mg.

7 0
3 years ago
The resistance of a wire depends on
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Answer:

b

Explanation:

because all are factors that determine the resistivity of a material

6 0
3 years ago
A 2290 kg car traveling to the west at 22.3 m/s slows down uniformly. How long would it take the car to come to a stop if the fo
Elina [12.6K]

Answer:

5.72 s

Explanation:

From Newton's law, F = ma

The East is +ve direction, Hence,

F = +8930 N

m = 2290 kg

a = ?

8930 = 2290 × a

a = 8930/2290 = 3.90 m/s²

So, we will find the time it takes the car to stop using the equations of motion

a = 3.90 m/s²

u = initial velocity of the car = - 22.3 m/s (the velocity is to the west)

v = final velocity of the car = 0 m/s (since the car comes to rest)

t = time taken for the car to come to rest = ?

v = u + at

0 = - 22.3 + (3.90)(t)

3.9t = 22.3

t = 5.72 s

5 0
3 years ago
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4. Who was the proponent of the Neo-classicism? a) Claude Debussy b) Joseph Maurice Ravel c) Igor Stravinsky d) Arnold Schoenber
nirvana33 [79]

Who was the proponent of the Neo-classicism?

a) Claude Debussy

b) Joseph Maurice Ravel

c) Igor Stravinsky

d) Arnold Schoenberg

4 0
3 years ago
A driver in a 2290-kg car car traveling at 42.7 m/s slams on the brakes and skids to a stop. If the coefficient of friction betw
8_murik_8 [283]

Answer:

126.56 m

Explanation:

Applying,

-F = ma............. Equation 1

Where F = frictional force, m = mass of the car, a = acceleration.

Note: Frictional force is negative because it act in opposite direction to motion

But,

F = mgμ.......... Equation 2

Where g = acceleration due to gravity, μ = coefficient of friction

Substitute equation 2 in equation 1

-mgμ = ma

a = -gμ.............. Equation 3

From the question,

Given: μ = 0.735

Constant: 9.8 m/s²

Substitute these values in equation 3

a = -9.8×0.735

a = -7.203 m/s²

Finally,

Applying

v² = u²+2as.............. Equation 4

Where v = final velocity, u = initial velocity, s = distance

From the question,

Given: u = 42.7 m/s, v = 0 m/s (to a stop), a = -7.203 m/s²

Substitute these values into equation 4

0² = 42.7²+2(-7.203)s

-1823.29 = -14.406s

s = -1823.29/-14.406

s = 126.56 m

4 0
3 years ago
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