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musickatia [10]
3 years ago
6

Suppose an electrical wire is replaced with one having every linear dimension doubled (i.e. the length and radius have twice the

ri original values). The wire now has ... a resistance which depends only on the material. the same resistance as before. less resistance than before. a resistance which can't be further predicted with the given information. more resistance than before.
Physics
1 answer:
saul85 [17]3 years ago
7 0

Answer:

The wire now has less (the half resistance) than before.

Explanation:

The resistance in a wire is calculated as:

R=\alpha \frac{l}{s}

Were:

R is resistance

\alpha is the resistance coefficient

l is the length of the material

s is the area of the transversal wire, in the case of wire will be circular area (s=\pi r^{2}).

So if the lenght and radius are doubled, the equation goes as follows:

R=\alpha \frac{l}{\pi r^{2} } =\alpha \frac{2l}{\pi {(2r)}^{2} } =\alpha \frac{2l}{\pi 4 {r}^{2} }=\frac{1}{2} \alpha \frac{l}{\pi r^{2} }

So finally because the circular area is a square function, the resulting equation is half of the one before.

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A stone is dropped into a river from a bridge at a height h above the water. Another stone is thrown vertically down at a time t
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Answer:

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Explanation:

We will apply the equations of kinematics to both stones separately.

First stone:

Let us denote the time spent after the second stone is thrown as 'T'.

y - y_0 = v_{y_0}(t+T) + \frac{1}{2}a(t+T)^2\\0 - h = 0 + \frac{1}{2}(-g)(t+T)^2\\(t+T)^2 = \frac{2h}{g}\\T = \sqrt{\frac{2h}{g}}-t

Second stone:

y - y_0 = v_{y_0}T + \frac{1}{2}aT^2\\0 - h = v_{y_0}T -\frac{1}{2}gT^2\\-h = v_{y_0}(\sqrt{\frac{2h}{g}} - t) - \frac{g}{2}(\sqrt{\frac{2h}{g}} - t)^2\\-h = v_{y_0}(\sqrt{\frac{2h}{g}} - t) - \frac{g}{2}(\frac{2h}{g} + t^2 - 2t\sqrt{\frac{2h}{g}})\\-h = v_{y_0}\sqrt{\frac{2h}{g}} - v_{y_0}t - h -\frac{g}{2}t^2 + gt\sqrt{\frac{2h}{g}}\\v_{y_0}(\sqrt{\frac{2h}{g}} - t) = \frac{g}{2}t^2 - gt\sqrt{\frac{2h}{g}}\\v_{y_0} = \frac{\frac{g}{2}t(t - 2\sqrt{\frac{2h}{g}})}{\sqrt{\frac{2h}{g}} - t}

6 0
3 years ago
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Elements with atomic numbers 58 through 71 are part of what series?
maria [59]

Elements with atomic numbers from 58 through 71 are part of the

<span>lanthanide</span> series <span />

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Answer:

<h2>E. 3.95kW</h2>

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Power = mgd/t (F = mg)

m = mass of the sand in kg

g = acceleration due to gravity in m/s²

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Power = 2000*9.8*12/60

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Minimum rate of power that must be supplied to this machine is 3920Watts or 3.92kW

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When someone lifts a book from the ground, the work you use is positive. By lifting the book, you change it's energy and it's original place The book gains, kinectic energy.


Hope I helped.

 

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