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alexandr402 [8]
2 years ago
12

The tungsten filament of a light bulb has an operating temperature of about 2 100 K. If the emitting area of the filament is 1.0

cm2, and its emissivity is 0.68, what is the power output of the light bulb? (σ = 5.67 × 10−8W/m2⋅K4)
a. 100 Wb. 75 Wc. 60 Wd. 40 W
Physics
1 answer:
Murljashka [212]2 years ago
5 0

Answer:

75 W

Explanation:

T = temperature of the filament = 2100 K

A = Emitting area of the filament = 1 cm² = 10⁻⁴ m²

e = Emissivity = 0.68

\sigma = Stefan's constant = 5.67 x 10⁻⁸ Wm⁻²K⁻⁴

Using Stefan's law, Power output of the light bulb is given as

P = \sigma e AT^{4} \\P = (5.67\times10^{-8}) (0.68) (10^{-4}) (2100)^{4}\\P = 75 W

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What resistance must be connected in parallel with a 633-Ω resistor to produce an equivalent resistance of 205 Ω?
alukav5142 [94]

Answer:

303 Ω

Explanation:

Given

Represent the resistors with R1, R2 and RT

R1 = 633

RT = 205

Required

Determine R2

Since it's a parallel connection, it can be solved using.

1/Rt = 1/R1 + 1/R2

Substitute values for R1 and RT

1/205 = 1/633 + 1/R2

Collect Like Terms

1/R2 = 1/205 - 1/633

Take LCM

1/R2 = (633 - 205)/(205 * 633)

1/R2 = 428/129765

Take reciprocal of both sides

R2 = 129765/428

R2 = 303 --- approximated

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2 years ago
A coin is placed on a large disk which rotates uniformly at a rate of 1 rot/s. The coefficient of friction between the coin and
s2008m [1.1K]

Answer:

r = 0.02 m

Explanation:

from the question we have :

speed = 1 rps = 1x 60 = 60 rpm

coefficient of friction (μ) = 0.1

acceleration due to gravity (g) = 9.8 m/s^{2}

maximum distance without falling off (r) = ?

to get how far from the center of the disk the coin can be placed without having to slip off we equate the formula for the centrifugal force with the frictional force on the turntable force

mv^2 / r =  m x g x μ

v^2 / r =  g x μ  .......equation 1

where

velocity (v) = angular speed (rads/seconds) x radius

angular speed (rads/seconds) = (\frac{2π}{60} ) x rpm

angular speed (rads/seconds) = (\frac{2 x π}{60} ) x 60 = 6.28 rads/ seconds

now

velocity = 6.28 x r = 6.28 r

now substituting the value of velocity into equation 1

v^2 / r =  g x μ

(6.28r)^2 / r = 9.8 x 0.1

39.5 x r = 0.98

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2 years ago
If the truck has a mass of 2,000 kilograms , what's its momentum?(v=35 m/s)
katen-ka-za [31]

Answer:

\boxed {\boxed {\sf  70,000 \ kg*m/s}}

Explanation:

Momentum is the product of mass and velocity.

p=m*v

The mass of the truck is 2,000 kilograms and the velocity is 35 meters per second.

m= 2000 \ kg \\v= 35 \ m/s

Substitute the values into the formula and multiply.

p= 2000 \ kg * 35 \ m/s \\p= 70,000 \ kg*m/s

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Scientist who discovered that the nucleus contains neutrons in addition to protons.
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Answer: James Chadwick

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