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brilliants [131]
3 years ago
7

A pendulum is constructed from a heavy metal rod and a metal disk, both of uniform mass density. The center of the disk is bolte

d to one end of the rod, and the pendulum hangs from the other end of the rod. The rod has a mass of =1.0 kg and a length of =49.8 cm. The disk has a mass of =4.0 kg and a radius of =24.9 cm. The acceleration due to gravity is =9.8 m/s2.
The pendulum is held with the rod horizontal and then released. What is the magnitude of its angular acceleration at the moment of release?
Physics
1 answer:
Setler79 [48]3 years ago
5 0

Answer: α = 20.4 rad/s²

Explanation:

α = τ/I

If we model it as a rod and a point mass, the moment of inertia

I = mL²/3 + ML² = 0.498²)(1.0/3 + 4.0) = 1.07 kg•m²

torque will be

τ = 1.0(9.8)(0.498/2) + 4.0(9.8)(0.498) = 21.96 N•m

α = 21.96 / 1.07 = 20.43...

Another possibility is that we model the large mass as a disc and apply the parallel axis theorem

I = mL²/3 + ½MR² + ML²

I =  1.07 + ½(4.0)0.249² = 1.19 kg•m/s

then

α = 18.45... 18.5 rad/s²

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vekshin1

Answer:

20 or 12

Explanation:

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3 0
3 years ago
When a wave hits a boundary, what determines how much is reflected and refracted?
Dafna1 [17]

Answer:

Angle and speed of wave

Explanation:

The two phenomena involved here are:

- Reflection: reflection occurs when a light wave bounces off the interface between two mediums, returning into the first medium, at a different angle

- Refraction: refraction occurs when a light wave passes through the interface between the two mediums, passing into the second medium, changing direction and speed

The coefficient of reflection tells what is the fraction of the wave that is reflected over the total; it is calculated as

R=|\frac{n_1 cos \theta_1 - n_2 cos \theta_2}{n_1 cos \theta_1 + n_2 cos \theta_2}|^2

where

n_1, n_2 are the index of refraction of the 1st and 2nd medium

\theta_1, \theta_2 are the angle between the ray of light  and the normal to the interface in the 1st and 2nd medium

From the formula, we see that the % of wave that is reflected depends on the angle and the index of refraction. Moreover, the index of refraction is related to the speed of the wave by:

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Angle and speed of wave

5 0
3 years ago
The loudness level of a​ sound, D, in​ decibels, is given by the formula Upper D equals 10 log (10 Superscript 12 Baseline Upper
svetoff [14.1K]

complete question

attached

Answer:

188.0 decibels

Explanation:

Substitute I = 6.3 x 10^6 into the given formula  

D(6.3 x 10^6) = 10log(10^12 x 6.3 x 10^6) = 188.0 to one decimal place.  

This is greater than 160 decibels, so the sound could rupture the human eardrum.  

Substitute I = 6.3 x 10^6 into the given formula  

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Katen [24]

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g Warm water in a geothermal heating system enters the pipe of a radiator at 20 psia and 119oF with a flow rate of 235 cfm (ft3/
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Answer:

See explanation

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f) Determine the Coefficient of Performance of the hot water heater [COPHW = 4.0] (defined as the heat absorbed by the hot water divided by the work done on the compressor)

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