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navik [9.2K]
3 years ago
11

A woman can read the large print in a newspaper only when it is at a distance of 55 cm or more from her eyes.

Physics
1 answer:
serious [3.7K]3 years ago
3 0

Answer:

Farsightedness (hyperopic)

2.79 D

Explanation:

When a person cannot see something which is close to their eyes this condition is known as farsightedness. She should use a convex lens to correct her eye sight.

u = Object distance =  22-2.7 = 19.3 cm

v = Image distance = -55+2.7 = -52.3 cm

f = Focal length

\frac{1}{f}=\frac{1}{u}+\frac{1}{v}\\\Rightarrow \frac{1}{f}=\frac{1}{19.3}+\frac{1}{-52.3}\\\Rightarrow \frac{1}{f}=\frac{3300}{100939}\\\Rightarrow f=\frac{100939}{3300}=30.58\ cm

The power of a lens is given by

P=\frac{1}{f}\\\Rightarrow P=\frac{1}{0.358}=2.79\ D

The power of her glasses should be 2.79 D

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As the frequency of the ac voltage across a capacitor approaches zero, the capacitive reactance of that capacitor:___________.
sergij07 [2.7K]

Answer:

B) approaches infinity

Explanation:

The capacitive reactance of an AC capacitor is given by;

X_C = \frac{1}{\omega C } = \frac{1}{2\pi f C}

Where;

C is the capacitance

f is the frequency of the ac voltage

X_C = \frac{1}{\omega C} = \frac{1}{2\pi f C} \\\\X_C = \frac{1}{2\pi f C} \\\\X_C = \frac{1}{2\pi (0) C} \\\\X_C = \frac{1}{0} \\\\X_C = \ infinity

Therefore, as the frequency of the ac voltage across a capacitor approaches zero, the capacitive reactance of that capacitor approaches infinity.

The correct option is (B) approaches infinity

7 0
3 years ago
Modeled after the two satellites problem (slide 12 in Lecture13, Universal gravity), imagine now if the period of the satellite
ikadub [295]

Answer:

  R = 6.3456 10⁴  mile

Explanation:

For this exercise we will use Newton's second law where force is gravitational force

      F = m a

The satellite is in a circular orbit therefore the acceleration is centripetal

      a = v² / r

Where the distance is taken from the center of the Earth

     G m M / r² = m v² / r

     G M / r = v²

The speed module is constant, let's use the uniform motion relationships, with the length of the circle is

     d = 2π  r

     v = d / t

The time for a full turn is called period (T)

Let's replace

     G M / r = (2π r / T)²

     r³ = G M T²²2 / 4π²

     r = ∛ (G M T² / 4π²)

We have the magnitudes in several types of units

      T = 88.59 h (3600 s / 1h) = 3.189 10⁵ s

      Re = 6.37 10⁶ m

Let's calculate

     r = ∛ (6.67 10⁻¹¹ 5.98 10²⁴ (3,189 10⁵)²/4π²)

     r = ∛ (1.027487 10²⁴)

     r = 1.0847 10⁸ m

This is the distance from the center of the Earth, the distance you want the surface is

     R = r - Re

     R = 108.47 10⁶ - 6.37 10⁶

     R = 102.1 10⁶ m

Let's reduce to miles

      R = 102.1 10⁶ m (1 mile / 1609 m)

     

      R = 6.3456 10⁴  mile

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3 years ago
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3 years ago
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vekshin1

Answer:

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Answer:

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Explanation:

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