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2 years ago

A tightly sealed glass jar is an example of which type of system?

2 answers:

7 0

Thermal expansion and contraction, specifically the different coefficients of thermal expansion between glass & metal is a closed system ; D

noname [10]2 years ago

4 0

D. hope it helps. :D

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The process of changing a property of a wave to transmit information is called .

BARSIC [14]

Answer : The process of changing a property of a wave to transmit information is called Modulation.

Explanation :

Modulation is the process of changing the property of wave to transmit information. This is done with the help of modulator.

In modulation, the message signal is superimposed on a high frequency signal. A sine wave ( usually high frequency ) is used as a high frequency carrier wave.

Modulation can be done in many ways like :

(1) Frequency modulation

(2) Amplitude modulation

(3) Pulse modulation

8 0

2 years ago

Read 2 more answers

A cup of hot coffee initially at 95 degrees C cools to 80 degrees C in 5 min while sitting in a room of temperature 21 degrees C

Oksana_A [137]

Answer:

When the temperature of the coffee is 50 °C, the time will be 20.68 mins

Explanation:

Given;

The initial temperature of the coffee T₀ = 95 °C

The temperature of the room = 21°C

Let T be the temperature at time of cooling t in mins

According to Newton's law of cooling;

$\frac{dT}{dt} \alpha (T-21)\\\\\frac{dT}{dt} = k (T-21)\\\\\frac{dT}{T-21} = kdt\\\\\int\limits {\frac{dT}{T-21}} = \int\limits kdt\\\\Log(T-21) =kt + Logc \\\\Log (\frac{T-21}{c} ) = kt\\\\T -21 = ce^{kt}\\\\At \ t = 0, T = 95\\\\95-21 = ce^0\\\\74 = c\\\\New, equation: T -21 = 74e^{kt}\\\\Again; when \ t= 5\ min, T = 80\\\\80 -21 = 74e^{5k}\\\\59 = 74e^{5k}\\\\e^{5k} = \frac{59}{74}\\\\ 5k = ln(\frac{59}{74})\\\\5k = -0.2265\\\\k = -0.0453$

When the temperature is 50 °C, the time t in min is calculated as;

$T -21 = 74e^{-0.0453t}\\\\50 -21 = 74e^{-0.0453t}\\\\29 = 74e^{-0.0453t}\\\\\frac{29}{74} = e^{-0.0453t}\\\\0.39189 = e^{-0.0453t}\\\\ln(0.39189 ) = {-0.0453t}\\\\-0.93677 = {-0.0453t}\\\\t = \frac{-0.93677}{-0.0453}\\\\ t = 20.68 \ mins$

Therefore, when the temperature of the coffee is 50 °C, the time will be 20.68 mins

4 0

2 years ago

The mass of Venus is 81.5% that of the earth, and its radius is 94.9% that of the earth. If a rock weighs 75.0 N on earth, compu

IgorLugansk [536]

Answer:

g = 0.905 gE

W = 67.9 N

Explanation:

given data

mass of Venus mv = 81.5% = 0.815

radius Rv = 94.9% = 0.949

weighs W = 75.0 N

solution

we apply here acceleration due to gravity at earth surface that is

g = $\frac{Gm}{R^2}$ = 9.80 m/s² ............1

g = $\frac{G(0.815)}{0.949R^2}$

g = 0.905 gE

and

W = m gv

W = 0.905 m gE

W = 0.905 × 75

W = 67.9 N

7 0

2 years ago

A 1.25 in. by 3 in. rectangular steel bar is used as a diagonal tension member in a bridge truss. the diagonal member is 20 ft l

pentagon [3]

Answer:

axial stress in the diagonal bar =36,000 psi

Explanation:

Assuming we have to find axial stress

Given:

width of steel bar: 1.25 in.

height of the steel bar: 3 in

Length of the diagonal member = 20ft

modulus of elasticity E= 30,000,000 psi

strain in the diagonal member ε = 0.001200 in/in

Therefore, axial stress in the diagonal bar σ = E×ε

= 30,000,000 psi× 0.001200 in/in =36,000 psi

5 0

2 years ago

An object is traveling at a constant velocity of 15 m/s when it experiences a constant acceleration of 3.5 m/s2 for a time of 11

Luda [366]

Vf=Vi+at=15m/s+(3.5m/s^2)(11s)=53.5m/s

7 0

2 years ago