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4 years ago

6

_______ are different forms of a single element. A) Atoms B) Elements C) Ions D) Isotopes

2 answers:

KiRa [710]4 years ago

8 0

D they have the same number of protons but a different number of neutrons.

ELEN [110]4 years ago

7 0

The answer is D. Isotopes.
Hope that helped.

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A spotlight on the ground shines on a wall 12 m away. If a man 2 m tall walks from the spotlight toward the building at a speed

mafiozo [28]

Answer:

0.6375 m/s

Explanation:

Let x be the distance of the man from the building

from the figure attached

initially the value of x=12

Given:

$\frac{dx}{dt}=-1.7m/s$

where the negative sign depicts that the distance of the man from the building is decreasing.

Now, Let The length of the shadow be = y

we have to calculate $\frac{dy}{dt}$ when x=4

from the similar triangles

we have,

$\frac{2}{12-x}=\frac{y}{12}$

or

$y=\frac{24}{12-x}$

Differentiating with respect to time 't' we get

$\frac{dy}{dt}=-\frac{24}{12-x}^2\frac{-dx}{dt}$

or

$\frac{dy}{dt}=\frac{24}{12-x}^2\frac{dx}{dt}$

Now for x = 4, and $\frac{dx}{dt}=-1.7m/s$ we have,

$\frac{dy}{dt}=\frac{24}{12-4}^2\times (-1.7)$

or

$\frac{dy}{dt}=-0.6375m/s$

<u>here, the negative sign depicts the decrease in length and in the question it is asked the decreasing rate thus, the answer is </u><u>0.6375m/s</u>

4 0

3 years ago

Thermopane window is constructed, using two layers of glass 4.0 mm thick, separated by an air space of 5.0 mm.

Bond [772]

To solve this problem it is necessary to apply the concepts related to rate of thermal conduction

$\frac{Q}{t} = \frac{kA\Delta T}{d}$

The letter Q represents the amount of heat transferred in a time t, k is the thermal conductivity constant for the material, A is the cross sectional area of the material transferring heat, $\Delta T$ , T is the difference in temperature between one side of the material and the other, and d is the thickness of the material.

The change made between glass and air would be determined by:

$(\frac{Q}{t})_{glass} = (\frac{Q}{t})_{air}$

$k_{glass}(\frac{A}{L})_{glass} \Delta T_{glass} = k_{air}(A/L)_{air} \Delta T_{air}$

$\Delta T_{air} = (\frac{k_{glass}}{k_{air}})(\frac{L_{air}}{L_{glass}}) \Delta T_{glass}$

$\Delta T_{air} = (\frac{0.84}{0.0234})(\frac{5}{4}) \Delta T_{glass}$

$\Delta T_{air} = 44.9 \Delta T_{glass}$

There are two layers of Glass and one layer of Air so the total temperature would be given as,

$\Delta T = \Delta T_{glass} +\Delta T_{air} +\Delta T_{glass}$

$\Delta T = 2\Delta T_{glass} +\Delta T_{air}$

$20\°C = 46.9\Delta T_{glass}$

$\Delta T_{glass} = 0.426\°C$

Finally the rate of heat flow through this windows is given as,

$\Delta {Q}{t} = k_{glass}\frac{A}{L_{glass}}\Delta T_{glass}$

$\Delta {Q}{t} = 0.84*24*10 -3*0.426$

$\Delta {Q}{t} = 179W$

Therefore the correct answer is D. 180W.

3 0

3 years ago

3. A bunny and a tortoise start a race from rest. The bunny accelerates at a rate ab for a time to until it reaches its

Aleks [24]

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heart

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follow

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tiktok

Answer:

yan

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answer

7 0

3 years ago

Which factor is most important in determining climate?

alisha [4.7K]

Temperature. The other three dont have anything to do with determining climate

8 0

3 years ago

Read 2 more answers

what would the mass be of an object that was moving at a velocity of 35 m/s and has a kinetic energy of 500j be?

bearhunter [10]

Answer:

0.816 kg

Explanation:

$E_k=\frac{1}{2}mv^{2}\\$

so $m=\frac{2E_k}{v^2}=\frac{2\times500}{35^2}=0.816 kg$

5 0

2 years ago