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3 years ago

Which describes the correct energy conversion when a solar cell is used to light a street lamp?

Physics

2 answers:

Zinaida [17]3 years ago

7 0

I think its A Solar to light

Lady_Fox [76]3 years ago

3 0

I think it's a solar power might seem strange or futuristic but it's already quite common place you might have a solar powered quartz watch on your wrist or solar powered pocket calculator

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What does convection mean

Sladkaya [172]

Convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat

4 0

3 years ago

Two cylindrical resistors are made from the same material. The shorter one has length L, diameter D, and resistance R1. The long

nordsb [41]

Answer:

the resistance of the longer one is twice as big as the resistance of the shorter one.

Explanation:

Given that :

For the shorter cylindrical resistor

Length = L

Diameter = D

Resistance = R1

For the longer cylindrical resistor

Length = 8L

Diameter = 4D

Resistance = R2

So;

We all know that the resistance of a given material can be determined by using the formula :

$R = \dfrac{\rho L }{A}$

where;

A = πr²

$R = \dfrac{\rho L }{\pi r ^2}$

For the shorter cylindrical resistor ; we have:

$R = \dfrac{\rho L }{\pi r ^2}$

since 2 r = D

$R = \dfrac{\rho L }{\pi (\frac{2}{2 \ r}) ^2}$

$R = \dfrac{ 4 \rho L }{\pi \ D ^2}$

For the longer cylindrical resistor ; we have:

$R = \dfrac{\rho L }{\pi r ^2}$

since 2 r = D

$R = \dfrac{ \rho (8 ) L }{\pi (\frac{2}{2 \ r}) ^2}$

$R = \dfrac{32\rho L }{\pi \ (4 D) ^2}$

$R = \dfrac{2\rho L }{\pi \ (D) ^2}$

Sp;we can equate the shorter cylindrical resistor to the longer cylindrical resistor as shown below :

$\dfrac{R_s}{R_L} = \dfrac{ \dfrac{ 4 \rho L }{\pi \ D ^2}}{ \dfrac{2\rho L }{\pi \ (D) ^2}}$

$\dfrac{R_s}{R_L} ={ \dfrac{ 4 \rho L }{\pi \ D ^2}}* { \dfrac {\pi \ (D) ^2} {2\rho L}}$

$\dfrac{R_s}{R_L} =2$

${R_s}=2{R_L}$

Thus; the resistance of the longer one is twice as big as the resistance of the shorter one.

7 0

3 years ago

An 805-kg race car can drive around an unbanked turn at a maximum speed of 54 m/s without slipping. the turn has a radius of cur

SIZIF [17.4K]

(a) Equating centripetal force to friction force, one finds the relation
v² = kar
for car speed v, coefficient of friction k, radius of curvature r, and downward acceleration a.

There is already downward acceleration due to gravity. The additional accceleration due to the wing is
a = F/m = 10600 N/(805 kg) ≈ 13.1677 m/s²
We presume this is added to the 9.80 m/s² gravity provides, so the coefficient of friction is
k = v²/(ar) = (54 m/s)²/((13.1677 m/s² +9.80 m/s²)·(155 m))
k ≈ 0.8191

(b) The maximum speed is proportional to the square root of the downward acceleration. Changing that by a factor of 9.80/(9.80+13.17) changes the maximum speed by the square root of this factor.
max speed with no wing effect = (54 m/s)√(9.8/22.97) ≈ 35.27 m/s

8 0

3 years ago

An astronaut is out in space with an extremely precise timing device measuring the speed of various fast‑moving objects. A laser

Leviafan [203]

Answer and Explanation:

with reference to Einstein's theory of special relativity, the speed of an electromagnetic radiation, here, laser will not change in any inertial frame or remains same irrespective of any change in inertial frame.

Therefore, the speed of light measured in both the cases, i.e., in astronaut's reference frame and spaceship's reference frame will be equal to the speed of light in vacuum, i.e., $3\times 10^{8} m/s$ .

The laser gun's speed in astronaut's reference frame is the same as the speed of the spaceship as it mounted on it, i.e., the speed of the laser gun is 200 million m/s.

The laser gun's speed measured in spaceship's reference frame will be zero, as it is mounted on the spaceship and is stationary in the spaceship's reference frame.

5 0

3 years ago

On a cosmic calendar, in which the history of the universe is compressed into one year, how long is the average human life span?

netineya [11]

Answer:

If one were to use 5 billion years as the age of the universe and 75 years as the average human life span then

T = 75 / 5 E9 = 1.5E-8

The number of seconds in a year is 3600 * 24 * 365 = 3.2E7

If t = N * T seconds in a year * fraction of human life span

t = 1.5E-8 * 3.2E7 = .48

A human life span is about 1/2 second compared to the life of the universe if the universe were compressed to a single year

8 0

2 years ago