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galben [10]
3 years ago
11

The lifetime (in hours) of a 60-watt light bulb is a random variable that has a Normal distribution with σ = 30 hours. A random

sample of 25 bulbs put on test produced a sample mean lifetime of = 1038 hours. If in the study of the lifetime of 60-watt light bulbs it was desired to have a margin of error no larger than 6 hours with 99% confidence, how many randomly selected 60-watt light bulbs should be tested to achieve this result?
Physics
1 answer:
attashe74 [19]3 years ago
5 0

Answer:

They must have about 166 randomly 60 watt light bulbs to achieve the result

N = 166

Explanation:

σ = 30

% 99 = 2.576

Using the standard equation of statistics knowing the difference between the measurement have a margin error no larger than 6 can solve

σ = √∑ ( x - z' )²  / N

Solve to N

N = ( % * σ  / Δ x  ) ²

N = ( 2.576 * 30 / 6 )²

N = 12.88 ²

N = 165. 89 44 ≅ 166

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Answer:

option(d)

Explanation:

The frequency of a wave is the property of the source of wave.

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The frequency is defined as the number of waves coming out from the source in 1 second.

As the frequency of wave increases, the number of wave coming per second increases.

So, the number of waves passing by increases but the speed remains same.

Option (d)

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3 years ago
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kaheart [24]
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W=Fs
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8 0
3 years ago
Match the following. Column A 1. Torque 2. Centre of gravity 3. Plumb line Column B A. Line of centre of gravity B. Maximum cons
gregori [183]

Answer:

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8 0
3 years ago
(a) Calculate the self-inductance (in mH) of a 55.0 cm long, 10.0 cm diameter solenoid having 1000 loops.
DedPeter [7]

Explanation:

(a) We have,

Length of solenoid, l = 55 cm = 0.55 m

Diameter of the solenoid, d = 10 cm

Radius, r = 5 cm = 0.05 m

Number of loops in the solenoid is 1000.

(a) The self inductance in the solenoid is given by :

L=\dfrac{\mu_o N^2A}{l}

A is area

L=\dfrac{4\pi \times 10^{-7}\times (1000)^2\times \pi (0.05)^2}{0.55}\\\\L=0.0179\ H\\\\L=17.9\ mH

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3 years ago
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