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3 years ago

Is ice on a plate a physical or chemical change?

Physics

2 answers:

Mama L [17]3 years ago

8 0

A physical charge I think

zalisa [80]3 years ago

5 0

Chemical change I think

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Which phase of matter does not conduct heat well?

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Gases do not conduct heat well.

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The forces acting on this object are _______ and the net force is ________ Balanced, 0 N Balanced, 10 N Unbalanced, 10 N Unbalan

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1st Blank Answer: Balanced
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What are the three places where ribisomes occur in a cell

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3 years ago

An object in motion will have a speed which is a scaler , or ( blank ) which is a vector .

mylen [45]

Answer:

Velocity

Explanation:

Objects in motion usually have a speed which is scalar or velocity which is a vector.

A scalar quantity is one with magnitude but has no directional attribute.

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3 years ago

The photon energies used in different types of medical x-ray imaging vary widely, depending upon the application. Single dental

Alchen [17]

1. Single dental x-rays: $5.0\cdot 10^{-11}m$

The energy of the photon is

$E=25 keV = 25,000 eV$

Using the conversion factor

$1 eV=1.6\cdot 10^{-19} J$

we can convert it into Joules:

$E=(25,000 eV)(1.6\cdot 10^{-19}J/eV)=4\cdot 10^{-15} J$

The relationship between photon energy and wavelength is

$\lambda=\frac{hc}{E}$

where

$h=6.63\cdot 10^{-34} Js$ is the Planck constant

$c=3\cdot 10^8 m/s$ is the speed of light

E is the energy

Substituting into the formula, we find

$\lambda=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{4\cdot 10^{-15} J}=5.0\cdot 10^{-11}m$

2. Microtomography: $2.0\cdot 10^{-11} m$

The energy of these photons is 2.5 times greater, so

$E=(2.5)(4\cdot 10^{-15} J)=1\cdot 10^{-14} J$

And by applying the same formula used at point 1, we find the corresponding wavelength:

$\lambda=\frac{(6.63\cdot 10^{-34}Js)(3\cdot 10^8 m/s)}{1\cdot 10^{-14} J}=2.0\cdot 10^{-11}m$

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3 years ago