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Sunny_sXe [5.5K]
3 years ago
12

Which best describes the energy used to pluck guitar strings to make sound?

Physics
2 answers:
Dmitry [639]3 years ago
8 0
Kinetic as its using the energy the body has in motion  <span />
Kobotan [32]3 years ago
4 0
Kinetic energy is used to do this

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It is just as difficult to accelerate a car on a level horizontal surface on the Moon as it is here on Earth because
Citrus2011 [14]

Answer:

Mass of the car is independent of gravity

Explanation:

Here, we want to state the reason why even though we have the acceleration due to gravity absent on the moon, it is still difficult to accelerate a car on a level horizontal level on the moon.

The answer to this is that the mass of the car that we want to accelerate is independent of gravity.

Had it been that gravity has an effect on the mass of the said car, then we might conclude that it will not be difficult to accelerate the car on a horizontal surface on the moon.

But due to the fact that gravity has no effect on the mass of the car to be accelerated, then the problem we have on earth with accelerating the car is the same problem we will have on the moon if we try to accelerate the car on a horizontal level surface.

4 0
3 years ago
What is the focal length of the eye-lens system when viewing an object at infinity? assume that the lens-retina distance is 2.0
34kurt
The focal length of the eye-lens system will be exactly 2.0 cm. The lens thickness is altered depending on the distance of the object being viewed so that the focal length is ALWAYS equal to the lens-retina distance. If this is not true fr an individual, they need glasses :)
4 0
4 years ago
Air is compressed adiabatically in a piston-cylinder assembly from 1 bar, 300 K to 10 bar, 600 K. The air can be modeled as an i
julia-pushkina [17]

Answer:

1) the entropy generated is Δs= 0.0363 kJ/kg K

2) the minimum theoretical work is w piston = 201.219 kJ/kg

Explanation:

1) From the second law of thermodynamics applied to an ideal gas

ΔS = Cp* ln ( T₂/T₁) - R ln (P₂/P₁)

and also

k= Cp/Cv , Cp-Cv=R → Cp*( 1-1/k) = R → Cp= R/(1-1/k)= k*R/(k-1)

ΔS =  k*R/(k-1)* ln ( T₂/T₁) - R ln (P₂/P₁)

where R= ideal gas constant , k= adiabatic coefficient of air = 1.4

replacing values (k=1.4)

ΔS =  k*R/(k-1)* ln ( T₂/T₁) - R ln (P₂/P₁)

ΔS = 1.4/(1.4-1) *8.314 J/mol K * ln( 600K/300K) - 8.314 J/mol K *  ln (10 bar/ 1bar)

ΔS = 1.026 J/ mol K

per mass

Δs = ΔS / M

where M= molecular weight of air

Δs = 1.026 J/ mol K / 28.84 gr/mol = 0.0363 J/gr K = 0.0363 kJ/kg K

2) The minimum theoretical work input is carried out under a reversible process. from the second law of thermodynamics

ΔS =∫dQ/T =0 since Q=0→dQ=0

then

0 = k*R/(k-1)* ln ( T₂/T₁) - R ln (P₂/P₁)

T₂/T₁ = (P₂/P₁)^[(k-1)/k]

T₂ = T₁ * (P₂/P₁)^[(k-1)/k]

replacing values

T₂ = 300K * ( 10 bar/1 bar)^[0.4/1.4] = 579.2 K

then from the first law of thermodynamics

ΔU= Q - Wgas = Q + Wpiston ,

where ΔU= variation of internal energy , Wgas = work done by the gas to the piston , Wpiston  = work done by the piston to the gas

since Q=0

Wpiston = ΔU

for an ideal gas

ΔU= n*Cv*(T final - T initial)

and also

k= Cp/Cv , Cp-Cv=R → Cv*( k-1) = R → Cv= R/(k-1)

then

ΔU= n*R/(k-1)*(T₂  - T₁)

W piston = ΔU = n*R/(k-1)*(T₂  - T₁)

the work per kilogram of air will be

w piston = W piston / m = n/m*R/(k-1)*(T₂  - T₁)  = (1/M*) R/(k-1)*(T₂  - T₁)  ,

replacing values

w piston = (1/M*) R/(k-1)*(T₂  - T₁)  = 1/ (28.84 gr/mol)* 8.314 J/mol K /0.4 * ( 579.2 K - 300 K) = 201.219 J/gr = 201.219 kJ/kg

6 0
3 years ago
A truck is traveling at 27 m/s down the interstate highway where you are changing a flat tire. frequency of 185 Hz.
Reil [10]

Answer:

(a) the observed frequency is 200 Hz

(b) the observed frequency is 188 Hz.

Explanation:

speed of the truck, Vs = 27 m/s

frequency of the truck as it approaches, Fs = 185 Hz

(a) Apply Doppler effect to determine the frequency you will hear.

As the truck approaches you, the observed frequency will be higher than the source frequency because of decrease in distance.

F_s = F_o [\frac{V}{V_S + V} ]

Where;

Fo is the observed frequency which is the frequency you will hear.

V is speed of sound in air

F_s = F_o [\frac{V}{V_S + V} ]\\\\185 = F_o [\frac{340}{27 + 340} ]\\\\185 = F_o (0.926)\\\\F_o = \frac{185}{0.926}\\\\F_o = 199.78 \ Hz

F_o = 200 \ Hz

(b) Apply the following formula for a moving observer and a moving source;

F_o = F_s[\frac{V-V_o}{V} ](\frac{V}{V-V_S} )

The observed frequency is negative since you are driving away from the truck and the source frequency is also negative since it is driving towards you.

F_o = F_s[\frac{V-V_o}{V} ](\frac{V}{V-V_S} )\\\\F_o = 185[\frac{340-22}{340} ](\frac{340}{340-27} )\\\\F_o = 185(0.9353)(1.0863)\\\\F_o = 188 \ Hz

5 0
3 years ago
What type of volcano forms when there is a series of violent and gentle eruptions resulting in layering of lava and ash?
Bogdan [553]
A shield volcano will form
5 0
3 years ago
Read 2 more answers
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