Calculate the kinetic energy in joules of an automobile weighing 2135 lb and traveling at 55 mph. (1 mile = 1.6093 km, 1 lb = 45
1 answer:
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Answer:
Explanation:
The photoelectric effect consists of the emission of electrons (electric current) that occurs when light falls on a metal surface under certain conditions.
If the light is a stream of photons and each of them has energy, this energy is able to pull an electron out of the crystalline lattice of the metal and communicate, in addition, a kinetic energy.
<u>This is what Einstein proposed: </u>
Light behaves like a stream of particles called photons with an energy
(1)
Where:
is the Planck constant
is the frequency
Now, the frequency has an inverse relation with the wavelength :
(2)
Where is the speed of light in vacuum and
is the wavelength of the absorbed photons in the photoelectric effect.
Substituting (2) in (1):
(3)
So, the energy of the incident photon must be equal to the sum of the Work function
of the metal and the maximum kinetic energy
of the photoelectron:
(4)
Rewriting to find :
(5)
Where is the minimum amount of energy required to induce the photoemission of electrons from the surface of a metal, and its value depends on the metal:
(6)
Being the threshold wavelength (the minimum wavelength needed to initiate the photoelectric effect)
Substituting (3) and (6) in (5):
(7)
Substituting the known values:
>>>>>This is the maximum kinetic energy that ejected electrons must have when violet light illuminates the material
Answer:
145.91 m
Explanation:
Data provided in the the question:
Wavelength of radio wave,
Here, c is speed of radio wave in air = 3 × 10⁸ m/s
f is the frequency = 514 kHz = 514 × 10³ Hz
Thus,
Wavelength = (3 × 10⁸) ÷ (514 × 10³) m
or
Wavelength = 583.65 m
Thus,
The height of the antenna will be
= = 583.65 ÷ 4 m
= 145.91 m
Answer:
t = 1.084 s
s = 8.25 m
Explanation:
given,
height from where skate board start (h) = 1 m
speed = 7.6 m/s
we know
v² = u² + 2 g h
v² =7.6² + 2×9.81× 1
v = 8.79 m/s
t = 1.084 s
then horizontal distance
s = 8.25 m