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3 years ago

Need help ASAP

Physics

1 answer:

Ksenya-84 [330]3 years ago

4 0

Answer:

A, B and D

2. A

Explanation:

1.Which of the following statements about light waves is true? check all correct answers

A.They come from sources across space reason is that a light can travels form its source and its moves across the space

B.They travel in a straight line from their source reason is that the type of light that undergo these is called parallel ray of light

C.They can travel through any type of material reason not all materials light can penetrate through e.g wall

D.They can be reflected by some types of material reason is that some materals reflect light rays e.g polished mirror

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A hot-water stream at 80 ℃ enters a mixing chamber with a mass flow rate of 0.5 kg/s where it is mixed with a stream of cold wat

rewona [7]

Answer:

$\dot{m_{2}}=0.865 kg/s$

Explanation:

$\dot{m_1}= 0.5kg/s$

from steam tables , at 250 kPa, and at

T₁ = 80⁰C ⇒ h₁ = 335.02 kJ/kg

T₂ = 20⁰C⇒ h₂ = 83.915 kJ/kg

T₃ = 42⁰C ⇒ h₃ = 175.90 kJ/kg

we know

$\dot{m_{in}}=\dot{m_{out}}$

$\dot{m_{1}}+\dot{m_{2}}=\dot{m_{3}}$

according to energy balance equation

$\dot{m_{in}}h_{in}=\dot{m_{out}}h_{out}$

$\dot{m_{1}}h_{1}+\dot{m_{2}}h_{2}=\dot{m_{3}}h_{3}$

$\dot{m_{1}}h_{1}+\dot{m_{2}}h_{2}=(\dot{m_{1}}+\dot{m_{2}})h_{3}\\(0.5\times 335.02)+(\dot{m_{2}}\times 83.915)=(0.5+\dot{m_{2}})175.90\\\dot{m_{2}}=0.865 kg/s$

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4 years ago

The threshold of hearing is defined as the minimum discernible intensity of the sound. It is approximately 10âˆ’12w/m2. Find the

Monica [59]

Answer:

The distance d from the car at which the sound from the stereo can still be discerned = 97720.5 m

Explanation:

Sound intensity heard at distance is related to the distance with the relation = (power of sound at the source)/(surface area of the wall of an imaginary sphere at the distance in question)

I = P/4πd²

Assuming the car has 2 speakers,

P = 0.06 W × 2 = 0.12 W

d = ?

For the intensity of the least discernible sound,

I = 10⁻¹² W/m²

10⁻¹² = 0.12/4πd²

d = 97720.5 m

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3 years ago

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kvv77 [185]

Answer:

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Explanation:

willow ptarmigan

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valina [46]

Answer: D

Explanation:
Let us examine the given actions to see which ones generate heat and sound energy from mechanical energy.

A) Stretching a string.
The mechanical stretching creates tension in the string, which is released when the tension is removed. The generation of thermal or sound energy is minimal or negligible.

B) Squeezing a sponge ball
The sponge ball experiences compressive loading. This generates minimal or no heat and sound energy.

C) Throwing a ball upwards in the air
Air friction generates minimal or no heat at low velocities. At low velocities the pressure waves are too small to generate sound.

D) Striking a hammer on a nail.
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This is the correct situation.

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