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Lelechka [254]
3 years ago
9

What minimum number of 45 W lightbulbs must be connected in parallel to a single 240 V household circuit to trip a 50.0 A circui

t breaker? ____lightbulbs
Physics
1 answer:
Black_prince [1.1K]3 years ago
5 0

Answer:267

Explanation:

Given

Power of light bulbs is 45 W

and voltage applied is 240 V

Allowable current is 50 A

and P=\frac{V^2}{R}

R=\frac{V^2}{P}

R=\frac{240\times 240}{45}=1280 \Omega

and wire will trip if resistance drop below

R_{total}=\frac{240}{50}=4.8 \Omega

Therefore R_{total}=\frac{R}{n}

n=\frac{R}{R_{total}}=\frac{1280}{4.8}=266.667 \approx 267

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When a rocket is 4 kilometers high, it is moving vertically upward at a speed of 400 kilometers per hour. At that instant, how f
Y_Kistochka [10]

Answer:

The angle of elevation of the rocket is increasing at a rate of 48.780º per second.

Explanation:

Geometrically speaking, the distance between the rocket and the observer (r), measured in kilometers, can be represented by a right triangle:

r = \sqrt{x^{2}+y^{2}} (1)

Where:

x - Horizontal distance between the rocket and the observer, measured in kilometers.

y - Vertical distance between the rocket and the observer, measured in kilometers.

The angle of elevation of the rocket (\theta), measured in sexagesimal degrees, is defined by the following trigonometric relation:

\tan \theta = \frac{y}{x} (2)

If we know that x = 5\,km, then the expression is:

\tan \theta = \frac{y}{5}

And the rate of change of this angle is determined by derivatives:

\sec^{2}\theta \cdot \dot \theta = \frac{1}{5}\cdot \dot y

\frac{\dot \theta}{\cos^{2}\theta} = \frac{\dot y}{5}

\frac{\dot \theta\cdot (25+y^{2})}{25} = \frac{\dot y}{5}

\dot \theta = \frac{5\cdot \dot y}{25+y^{2}}

Where:

\dot \theta - Rate of change of the angle of elevation, measured in sexagesimal degrees.

\dot y - Vertical speed of the rocket, measured in kilometers per hour.

If we know that y = 4\,km and \dot y = 400\,\frac{km}{h}, then the rate of change of the angle of elevation is:

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The angle of elevation of the rocket is increasing at a rate of 48.780º per second.

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3 years ago
Two vectors have magnitudes of 10 and 15. The angle between them when they are drawn with their tails at the same point is 65. T
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Two vectors have magnitudes of 10 and 15. The angle between them when they are drawn with their tails at the same point is 65. The component of the longer vector along the line of the shorter is 6.33 .

A vector is a quantity or phenomenon that has two independent properties: magnitude and direction. The term also denotes the mathematical or geometrical representation of such a quantity. Examples of vectors in nature are velocity, momentum, force, electromagnetic fields, and weight.

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Describe which relationships in Ohm’s law are DIRECT and which are INVERSE. Use examples to support your answer. You can use cal
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