If the 5,500 J of sound and light is the ONLY useful output
from the phone, then the phone's efficiency is
(5,500J / 10,000J) = 0.55 = 55% .
But the test engineer forgot one little minor almost insignificant detail.
As a test engineer myself, I'd say that he needs to turn in his laptop
and soldering iron, and think about changing his career to a job for
which he may be better suited, like 8 hours a day in a highway toll-booth.
What about that little radio transmitter and receiver inside the phone,
that maintain digital RF communication with the nearest cell tower ?
Without that microscopic radio transceiver ... plus 30 or 40 apps
that are always running unless you shut them off ... the device in your
pocket is essentially a flat rock with one side that sometimes glows.
Answer:
vₐ = v_c
Explanation:
To calculate the escape velocity let's use the conservation of energy
starting point. On the surface of the planet
Em₀ = K + U = ½ m v_c² - G Mm / R
final point. At a very distant point
Em_f = U = - G Mm / R₂
energy is conserved
Em₀ = Em_f
½ m v_c² - G Mm / R = - G Mm / R₂
v_c² = 2 G M (1 /R - 1 /R₂)
if we consider the speed so that it reaches an infinite position R₂ = ∞
v_c =
now indicates that the mass and radius of the planet changes slightly
M ’= M + ΔM = M (
)
R ’= R + ΔR = R (
)
we substitute
vₐ =
let's use a serial expansion
√(1 ±x) = 1 ± ½ x +…
we substitute
vₐ = v_ c (
)
we make the product and keep the terms linear
vₐ = v_c
Answer:
the weight of the object decreases when it is taken from the Earth to the Moon
Explanation:
The weight of an object is defined as the product of the mass of the object with the acceleration due to gravity of the Planet.

where,
W = weight of the object
m = mass of the object
g = acceleration due to gravity on the planet
The mass of an object remains constant everywhere in the universe. Therefore, the weight is directly proportional to the value of acceleration due to gravity.
The value of acceleration due to gravity on the Moon is lesser than its value on the Earth.
<u>Hence, the weight of the object decreases when it is taken from the Earth to the Moon </u>
A prism will separate white light into a rainbow of light