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alexandr1967 [171]
3 years ago
6

Cell phones do not work everywhere. There are places where your cell phone cannot get a signal

Physics
2 answers:
Ilya [14]3 years ago
7 0

Answer:

D

Explanation:

cell phones must be close enough to a tower to send a receive electromagnetic waves

shusha [124]3 years ago
5 0
There are probably no strong signals
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What happens to a light ray passing through the center of a lens?
Readme [11.4K]
Theoretically, the light ray will not change direction. The center of a lens is called the optical center. If the ray of light hits the lens even just a little bit off center, the light ray is refracted. Refraction happens when the incident and exit angles of the ray are different. The optical center is guaranteed to not have any difference in angle, which allows the light ray to pass through directly without changing direction.
6 0
3 years ago
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A python can detect thermal radiation from objects that differ in temperature from their environment as long as the received int
yanalaym [24]

Answer:

10.52 m

Explanation:

The power radiated by a body is given by

P = σεAT⁴ where ε = emissivity = 0.97, T = temperature = 30 C + 273 = 303 K, A = surface area of human body = 1.8 m², σ = 5.67 × 10⁻⁴ W/m²K⁴

P = σεAT⁴ = 5.67 × 10⁻⁸ W/m²K⁴ ×  0.97 × 1.8 m² × (303)⁴ = 834.45 W

This is the power radiated by the human body.

The intensity I = P/A where A = 4πr² where r = distance from human body.

I = P/4πr²

r = (√P/πI)/2

If the python is able to detect an intensity of 0.60 W/m², with a power of 834.45 W emitted by the human body, the maximum distance r, is thus

r = (√P/πI)/2 = (√834.45/0.60π)/2 = 21.04/2 = 10.52 m

So, the maximum distance at which a python could detect your presence is 10.52 m.

3 0
3 years ago
A light horizontal spring has a spring constant of 138 N/m. A 3.35 kg block is pressed against one end of the spring, compressin
BARSIC [14]

Answer:

U_k = 0.113

Explanation:

using the law of the conservation of energy:

E_i -E_f=W_f

\frac{1}{2}Kx^2=NU_kd

where K is the spring constant, x is the spring compression, N is the normal force of the block, U_k is the coefficiet of kinetic friction and d is the distance.

Also, by laws of newton, N is calculated by:

N = mg

N = 3.35 kg * 9.81 m/s

N = 32.8635

So, Replacing values on the first equation, we get:

\frac{1}{2}(138)(0.123)^2= (32.8635)U_k(0.281m)

solving for U_k:

U_k = 0.113

8 0
3 years ago
I need help with science due tommorow
Andrews [41]
The first one is the light bends sheikh is known as refraction
8 0
3 years ago
While an emf source supplies energy to a circuit, that energy is dissipated when the current passes through resistance. In deali
fredd [130]

The question is incomplete, the options are;

RI^2

I^2/R

R/I^2

R/V^2

RV^2

V^2/R

VI

VIR

Select all that apply

Answer:

P=RI^2

P=V^2/R

P=VI

Explanation:

Power is the rate at which energy is changing in a circuit. It is shown by the formulas outlined above from the group of answer choices. Since the current (I), voltage (V), and resistance (R) were mentioned in the question, any of three three formulas could be used to obtain the power drawn by the conductor.

7 0
3 years ago
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