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4 years ago

When a substance undergoes a phase change it still has a definite....

Physics

1 answer:

Murljashka [212]4 years ago

6 0

It still has a definite temperature.

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When he reaches the bottom, 4.2 m below his starting point, his speed is 2.2 m/s . By how much has thermal energy increased duri

Advocard [28]

Complete question:

A fireman of mass 80 kg slides down a pole. When he reaches the bottom, 4.2 m below his starting point, his speed is 2.2 m/s. By how much has thermal energy increased during his slide?

Answer:

The thermal energy increased by 3,099.2 J

Explanation:

Given;

mass of the fireman, m = 80 kg

initial position of the fireman, hi = 4.2 m

final speed, v = 2.2 m/s

The change in the thermal energy is calculated as;

ΔE + (K.Ef - K.Ei) + (Uf - Ui) = 0

where;

ΔE is the change in the thermal energy

K.Ef is the final kinetic energy

K.Ei is the initial kinetic energy

Uf is the final potential energy

Ui is the initial potential energy

$\Delta E_{th} + (\frac{1}{2} mv_f^2 - \frac{1}{2} mv_i^2) + (mgh_f - mgh_i)=0\\\\initial \ velocity, \ v_i = 0\\final \ height , \ h_f = o\\\\\Delta E_{th} + (\frac{1}{2} mv_f^2) + ( - mgh_i)=0\\\\\Delta E_{th} + \frac{1}{2} mv_f^2 - mgh_i = 0\\\\\Delta E_{th} =mgh_i - \frac{1}{2} mv_f^2\\\\\Delta E_{th} = 80 \times 9.8 \times 4.2 \ \ - \ \ \frac{1}{2} \times 80 \times (2.2)^2 \\\\\Delta E_{th} = 3292.8 \ J \ - \ 193.6 \ J\\\\\Delta E_{th} = 3,099.2 \ J$

3 0

3 years ago

A spherical balloon is made from a material whose mass is 3.30 kg. The thickness of the material is negligible compared to the 1

stellarik [79]

Answer:

563712.04903 Pa

Explanation:

m = Mass of material = 3.3 kg

r = Radius of sphere = 1.25 m

v = Volume of balloon = $\frac{4}{3}\pi r^3$

M = Molar mass of helium = $4.0026\times 10^{-3}\ kg/mol$

$\rho$ = Density of surrounding air = $1.19\ kg/m^3$

R = Gas constant = 8.314 J/mol K

T = Temperature = 345 K

Weight of balloon + Weight of helium = Weight of air displaced

$mg+m_{He}g=\rho vg\\\Rightarrow m_{He}=\rho vg-m\\\Rightarrow m_{He}=1.19\times \frac{4}{3}\pi 1.25^3-3.3\\\Rightarrow m_{He}=6.4356\ kg$

Mass of helium is 6.4356 kg

Moles of helium

$n=\frac{m}{M}\\\Rightarrow n=\frac{6.4356}{4.0026\times 10^{-3}}\\\Rightarrow n=1607.85489$

Ideal gas law

$P=\frac{nRT}{v}\\\Rightarrow P=\frac{1607.85489\times 8.314\times 345}{\frac{4}{3}\pi 1.25^3}\\\Rightarrow P=563712.04903\ Pa$

The absolute pressure of the Helium gas is 563712.04903 Pa

3 0

3 years ago

The suspension system of a 1700 kg automobile "sags" 7.7 cm when the chassis is placed on it. Also, the oscillation amplitude de

spin [16.1K]

Answer:

the spring constant k = $5.409*10^4 \ N/m$

the value for the damping constant $\\ \\b = 1.518 *10^3 \ kg/s$

Explanation:

From Hooke's Law

$F = kx\\\\k =\frac{F}{x}\\\\where \ F = mg\\\\k = \frac{mg}{x}\\\\given \ that:\\\\mass \ of \ each \ wheel = 425 \ kg\\\\x = 7.7cm = 0.077 m\\\\g = 9.8 \ m/s^2\\\\Then;\\\\k = \frac{425 \ kg * 9.8 \ m/s^2}{0.077 \ m}\\\\k = 5.409*10^4 \ N/m$

Thus; the spring constant k = $5.409*10^4 \ N/m$

The amplitude is decreasing 37% during one period of the motion

$e^{\frac{-bT}{2m}}= \frac{37}{100}\\\\e^{\frac{-bT}{2m}}= 0.37\\\\\frac{-bT}{2m} = In(0.37)\\\\\frac{-bT}{2m} = -0.9943\\\\b = \frac{2m(0.9943)}{T}\\\\b = \frac{2m(0.9943)}{\frac{2 \pi}{\omega}}\\\\b = \frac{m(0.9943) \ ( \omega) )}{ \pi}$

$b = \frac{m(0.9943)(\sqrt{\frac{k}{m})}}{\pi}\\\\b = \frac{425*(0.9943)(\sqrt{\frac{5.409*10^4}{425}) } }{3.14}\\\\b = 1518.24 \ kg/s\\\\b = 1.518 *10^3 \ kg/s$

Therefore; the value for the damping constant $\\ \\b = 1.518 *10^3 \ kg/s$

5 0

3 years ago

Because the __ signal changes smoothly, like a sine wave, it can closely mimic a human voice. However, part of the signal can ea

Naya [18.7K]

Answer:

Analog,Noise,Digital,less

Explanation:

Analog signal changes continuously with time and moves smoothly.

Due to this analog signal can easily disturbed by noise.

Since digital signal are like square wave due to this digital signals are less affected by noise.

Because the Analog signal changes smoothly, like a sine wave, it can closely mimic a human voice. However, part of the signal can easily get lost to Noise. Because Digital signals are on or off, like a square wave, they best carry information that can easily be converted into numbers. These signals are less affected by noise.

7 0

3 years ago

If the oven is used for two hours to bake cookies how many kilowatt hours are used

LUCKY_DIMON [66]

. In 1 hour 2400 kilowatts are used. In 2 hours a total of 4800 kilowatts are used.

3 0

3 years ago