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# mairangi

Questions0
• ### matrix - infinitely solution?

which one of the following value of a gave infinitely many solutions?

• ### thermodynamics?

Physics2 months ago
• ### Oscillations and Waves?

On a day when the speed of sound in air is 344 m/s, two speakers are set up at a sports field, which has a surface that reflects almost no sound. The speakers are 1.6 m above the ground, 10 m apart, on the line at the end of the field. They emit sound that has a spherically symmetric intensity distribution.

(a) One of the speakers is set to emit sound at a frequency of 200 Hz and the other at 205 Hz with the same intensity.

(i) Describe the sound (pitch, intensity, time variation) heard by an observer at Location A, 50 m away (equidistant) from both speakers. (See Figure 4 below, which shows a bird's-eye view of the situation; not drawn to scale.)

(ii) Sketch a graph, showing a scale on each axis, accurately portraying the sound waves heard by the observer.

(b) The speakers are reset so that they both emit sound, perfectly in phase with one another and with the same intensity, at a frequency of 86 Hz. The observer stands at Location B, 24 m away from one of the speakers, directly in front of it (i.e., the line from the observer to the speaker is perpendicular to the line between the speakers). (See Figure 4 below, not drawn to scale.)

(i) Describe and explain what the observer would hear at Location B, justifying your answer with a simple calculation.

Physics2 months ago

• ### two distinct processes thermodynamics?

WATER/ICE SYSTEM

I - A sample of water is frozen by placing it in contact with a heat bath at 0 ◦C.II - An identical sample of water, which has been supercooled to −10 ◦C, freezeswhen it is given a slight mechanical shock.

Question 1:

For each of the two processes, I and II, explain why it can be considered to be either

reversible or irreversible.

Question 2:

For each of the two processes, I and II, determine the sign of the entropy change (positive: > 0, negative: < 0 or zero: = 0) for:

(i) the system

(ii) the surroundings

(iii) the Universe consisting of system plus surroundings

thank you very much

Physics2 months ago
• ### SHM- simple harmonic motion?

a) spring equilibrium length

b) amplitude of the particle’s oscillations?

c) particle’s maximum kinetic energy (approximately)?

d) What is the angular frequency ω of the oscillations if the mass of the particle is 367 g?

-------------------------------------------

where

PE = potential energy

TE= total energy

thanks

Physics2 months ago
• ### What is the power plant's thermal efficiency?

The electric output of a power plant is 800 MW . Cooling water flows through the power plant at the rate 0.900 ×108L/hr. The cooling water enters the plant at 13.0ºC and exits at 26.0ºC .

What is the power plant's thermal efficiency?

thanks

Physics2 months ago
• ### first and second law of thermodynamics?

Q1:

Which, if any, of the heat engines (possibly more than one) in the figure violate the first law of thermodynamics?

Option 1: Engine (a)

Option 2: Engine (b)

Option 3: Engine (c)

Option 4: None of the engines violate the first law of thermodynamics.

Q2:

Which, if any, of the heat engines (possibly more than one) in the figure violate the second law of thermodynamics?

Option 1: Engine (a)

Option 2: Engine (b)

Option 3: Engine (c)

Option 4: None of the engines violate the second law of thermodynamics.

Physics2 months ago
• ### does the mean free path change?

A monatomic gas is adiabatically compressed to 0.125 of its initial volume. How do the following quantities change:

By what factor does the mean free path change?

Physics2 months ago
• ### entropy change?

Consider the freezing of 1 kg of supercooled water at –10 °C. This is an irreversible

transformation of the water from an initial state (A, supercooled liquid at –10 °C) to a final state (D, ice at –10 °C). The heat of the spontaneous transformation A->D is –315Jg^–1.

Q1

What is the entropy change of the surroundings when 1 kg of supercooled water

freezes at –10 °C? [You may assume that the surroundings represent a large heat

bath, which absorbs and releases heat quasi-statically at –10 °C.]

Q2

Calculate the entropy change of 1 kg of water when it goes along a quasi-static

(“reversible”) path from State A to State D, passing through two intermediate states [B, water at 0 °C; and C, ice at 0 °C). [You may assume that the specific heat of supercooled water is the same as that of ordinary liquid water.]

thank u

info u may need:

Specific heat of water (temperature independent) cwater 4186 J kg^–1 K^–1

Latent heat of freezing of water (at 0 °C) Lf 333 J g^–1

Specific heat of ice (temperature independent) cice 2093 J kg^–1 K^–1

Chemistry2 months ago
• ### Calculate the entropy change?

Consider the freezing of 1 kg of supercooled water at –10 °C. This is an irreversible

transformation of the water from an initial state (A, supercooled liquid at –10 °C) to a final state (D, ice at –10 °C). The heat of the spontaneous transformation A->D is –315Jg^–1.

Q1

What is the entropy change of the surroundings when 1 kg of supercooled water

freezes at –10 °C? [You may assume that the surroundings represent a large heat

bath, which absorbs and releases heat quasi-statically at –10 °C.]

Q2

Calculate the entropy change of 1 kg of water when it goes along a quasi-static

(“reversible”) path from State A to State D, passing through two intermediate states [B, water at 0 °C; and C, ice at 0 °C). [You may assume that the specific heat of supercooled water is the same as that of ordinary liquid water.]

thank u

• ### thermodynamics, determine the mass of the neon?

To determine the mass of neon contained in a rigid 2.0-L cylinder, you vary the cylinder's temperature while recording the reading of a pressure gauge. Your data are as follows:

Temperature               Pressure gauge,

TC(∘C)                          pg(atm)

100                               6.52

150                               7.80

200                                8.83

250                                9.59

We need to work with absolute pressure and temperature, not gauge pressure or Celsius temperatures. Graphing either p versus T or T versus p gives a straight line. For the graph above, we chose to graph p versus T, and the gauge pressures in atmospheres were converted to absolute pressures in pascals. From the equation for the line of best fit given, determine the mass of the neon.

thank you

Physics3 months ago
• ### at what rate (in MW) must electrical energy be converted to heat to keep the process going in a steady-state?

In the final stage of producing heavy aluminium (Al) bars at the Bluff smelter near

Invercargill, molten aluminium is continuously poured from a very large bath into cylindrical moulds at a rate of 2 kg per second. The level of molten aluminium in the bath is maintained by dropping unformed, recently purified, solid aluminium into it at the same rate, 2 kg/s. The newly purified aluminium is at a temperature of 570 °C when it reaches the bath, and the temperature of the poured liquid aluminium is 720 °C.

Ignoring heat losses to the surroundings, at what rate (in MW) must electrical energy be converted to heat to keep the process going in a steady-state?

Thermal properties of Aluminium

melting point Tf = 660 °C

latent heat of fusion Lf = 10.8 kJ mol^–1

specific heat of solid cs = 0.91 kJ kg–1 K^–1

specific heat of liquid cl = 1.18 kJ kg–1 K^–1

molar mass MAl = 27.0 g mol^–1

thank you!

Physics3 months ago
• ### How do you identify a metal?

512 g of an unknown metal at a temperature of 15 ∘C is dropped into a 100 g aluminum container holding 325 g of water at 98 ∘C. A short time later, the container of water and metal stabilizes at a new temperature of 78 ∘C.

Identify the metal

B: Aluminium

C: iron

D: copper

thanks

• ### Find the energy?

Cold water at a temperature of 15 ◦C enters a heater, and the resulting hot water

has a temperature of 61 ◦C. A person uses 120 kg of hot water in taking a hot

shower.

(a) Find the energy needed to heat the water.

(b) Assuming that the utility company charges \$0.10 per kilowatt-hour for

electrical energy, determine the cost of heating the water.

• ### hollow cylinder inertia?

what is the hollow cylinder's inertia equation?

i know the solid cylinder is 1/2 mr^2

thanks

• ### thermo chem?

A surveyor has a steel measuring tape that is calibrated to be 100.000 m long (i.e., accurate to ±1 mm ) at 20 ∘C.

Part A:If she measures the distance between two stakes to be 75.175 m on a 9 ∘C day, does she need to add or subtract a correction factor to get the true distance?answer: She needs to subtract the correction factor to get the true distance.

How do you do part B?

Part B: (see image) the expansion coefficient for steel is 1.1*10^-5

• ### calculate the correlation factor?

A surveyor has a steel measuring tape that is calibrated to be 100.000 m long (i.e., accurate to ±1 mm ) at 20 ∘C.

Part A:If she measures the distance between two stakes to be 75.175 m on a 9 ∘C day, does she need to add or subtract a correction factor to get the true distance?answer: She needs to subtract the correction factor to get the true distance.

Part B: (see image)