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VashaNatasha [74]
2 years ago
8

PHYSICS!

Physics
1 answer:
Allushta [10]2 years ago
6 0

Answer:

Friction is useful in some cases like walking and cycling ..

but it is unwanted in machines as it create unwanted sounds and heat .,due to which we loss energy

Explanation:

mark me as brainliest ❤️

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Two polarizers A and B are aligned so that their transmission axes are vertical and horizontal, respectively. A third polarizer
Reptile [31]

Answer:

Explanation:

Let the angle between the first polariser and the second polariser axis is θ.

By using of law of Malus

(a)

Let the intensity of light coming out from the first polariser is I'

I' = I_{0}Cos^{2}\theta     .... (1)

Now the angle between the transmission axis of the second and the third polariser is 90 - θ. Let the intensity of light coming out from the third polariser is I''.

By the law of Malus

I'' = I'Cos^{2}\left ( 90-\theta \right )

So,

I'' = I_{0}Cos^{2}\theta Cos^{2}\left ( 90-\theta \right )

I'' = I_{0}Cos^{2}\theta Sin^{2}\theta

I'' = \frac{I_{0}}{4}Sin^{2}2\theta

(b)

Now differentiate with respect to θ.

I'' = \frac{I_{0}}{4}\times 2 \times 2 \times Sin2\theta \times Cos 2\theta

I'' = \frac{I_{0}}{2}\times Sin 4\theta

7 0
3 years ago
For a given initial projectile speed Vo, calculate what launch angle A gives the longest range R. Show your work, don't just quo
pickupchik [31]
The optimal angle of 45° for maximum horizontal range is only valid when initial height is the same as final height. 

<span>In that particular situation, you can prove it like this: </span>

<span>initial velocity is Vo </span>
<span>launch angle is α </span>

<span>initial vertical velocity is </span>
<span>Vv = Vo×sin(α) </span>

<span>horizontal velocity is </span>
<span>Vh = Vo×cos(α) </span>

<span>total time in the air is the the time it needs to fall back to a height of 0 m, so </span>
<span>d = v×t + a×t²/2 </span>
<span>where </span>
<span>d = distance = 0 m </span>
<span>v = initial vertical velocity = Vv = Vo×sin(α) </span>
<span>t = time = ? </span>
<span>a = acceleration by gravity = g (= -9.8 m/s²) </span>
<span>so </span>
<span>0 = Vo×sin(α)×t + g×t²/2 </span>
<span>0 = (Vo×sin(α) + g×t/2)×t </span>
<span>t = 0 (obviously, the projectile is at height 0 m at time = 0s) </span>
<span>or </span>
<span>Vo×sin(α) + g×t/2 = 0 </span>
<span>t = -2×Vo×sin(α)/g </span>

<span>Now look at the horizontal range. </span>
<span>r = v × t </span>
<span>where </span>
<span>r = horizontal range = ? </span>
<span>v = horizontal velocity = Vh = Vo×cos(α) </span>
<span>t = time = -2×Vo×sin(α)/g </span>
<span>so </span>
<span>r = (Vo×cos(α)) × (-2×Vo×sin(α)/g) </span>
<span>r = -(Vo)²×sin(2α)/g </span>

<span>To find the extreme values of r (minimum or maximum) with variable α, you must find the first derivative of r with respect to α, and set it equal to 0. </span>

<span>dr/dα = d[-(Vo)²×sin(2α)/g] / dα </span>
<span>dr/dα = -(Vo)²/g × d[sin(2α)] / dα </span>
<span>dr/dα = -(Vo)²/g × cos(2α) × d(2α) / dα </span>
<span>dr/dα = -2 × (Vo)² × cos(2α) / g </span>

<span>Vo and g are constants ≠ 0, so the only way for dr/dα to become 0 is when </span>
<span>cos(2α) = 0 </span>
<span>2α = 90° </span>
<span>α = 45° </span>
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What is being done about emission controls?
Licemer1 [7]
The original Clean Air Act of 1970 gave the US EPA board authority to regulate motor vehicle pollution and the agencies emission control policies and requirements have become progressively more stringent since then
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2 years ago
Evidence suggests that there may be _______ momentum and ________ reversal patterns in stock price behavior.
bearhunter [10]

CORRECT ANSWER:

D. short-run; long run

STEP-BY-STEP EXPLANATION:

The whole question from book is

Evidence suggests that there may be _______ momentum and ________ reversal patterns in stock price behavior.

A. short-run; short-run

B. long-run; long-run

C. long-run; short-run

D. short-run; long run

Evidence suggests that there may be <em><u>short-run</u></em> momentum and <em><u>long run </u></em>reversal patterns in stock price behavior.

8 0
3 years ago
This image below shows a ship using sonar to map the seafloor. pls help i need this :(
Umnica [9.8K]

Answer:

d and i think a?

Explanation:

im so sorry if its wrong

5 0
3 years ago
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