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shepuryov [24]
2 years ago
4

Many years ago, scientists and doctors had no idea what caused diseases in people. There were theories that people who succumbed

to disease had breathed bad air, had committed a bad deed, or even that they had bad blood, prompting doctors to let out some of their blood. During a cholera outbreak in London in 1854, John Snow, a London physician and scientist, mapped the location of the cholera victims. He was a skeptic of the "bad air" theory and proposed that a contaminated water source was the cause of the cholera outbreak. His map showed a cluster of early deaths around a particular water pump. The disease outbreak declined because the water pump was closed (by removing its handle) and because people had fled the area. His idea that the disease was caused by contaminated water was confirmed by an inspection of the well that discovered raw sewage had seeped into it. Which of the following is this the best example of?
Physics
1 answer:
luda_lava [24]2 years ago
8 0

Answer:

an instance in which scientific knowledge changed when new evidence was encountered

Explanation:

cuz this the answer i got on my test

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A thin ring of radius 73 cm carries a positive charge of 610 nC uniformly distributed over it. A point charge q is placed at the
kow [346]

Answer:

q = - 93.334 nC

Explanation:

GIVEN DATA:

Radius of ring  73 cm

charge on ring 610 nC

ELECTRIC FIELD p FROM CENTRE IS AT 70 CM

E  =  2000 N/C

Electric field due tor ring is guiven as

E = \frac{KQx}{[x^2+ R^2]^{3/2}}

E = \frac{9\time 10^9 \times 610\times 10^[-9} 0.70}{(0.70^2 + 0.73^2)^{3/2}}

E1 = 3714.672 N/C

electric field due to point charge q

E  =\frac[kq}{x^2}

E = \frac{9\times 10^9 \times q}{0.70^2}

E2 = 1.837\times 10^{10}\times q

now the eelctric charge at point P is

E = E1 + E22000 =  3714.672 + 1.837\times 10[10} \times q

solving for q

q = - 93.334 nC

7 0
2 years ago
A carbon-dioxide laser emits infrared light with a wavelength of 10.6 μm. What is the length of a tube that will oscillate in th
alex41 [277]

Answer:

The length of a tube and number of rounds are 0.848 m and 1.77\times10^{8}\ trip\ per\ second.

Explanation:

Given that,

Wavelength \lambda= 10.6\mu m

m = 160000

We need to calculate the length

Using formula of wavelength

Laser tube behave like closed pipe

m\dfrac{\lambda}{2}=L

L=160000\times\dfrac{10.6\times10^{-6}}{2}

L=0.848\ m

Distance traveled by pulse of light in one back and fourth trip

d=2L

d=2\times0.848

d=1.696\ m

We need to calculate the time

Using formula for time

t = \dfrac{d}{c}

t=\dfrac{1.696}{3\times10^{8}}

t=5.653\times10^{-9}\ s

We need to calculate the number of round

Using formula of number of round

N=\dfrac{1}{t}

N= \dfrac{1}{5.653\times10^{-9}}

N=1.77\times10^{8}\ trip\ per\ second

Hence, The length of a tube and number of rounds are 0.848 m and 1.77\times10^{8}\ trip\ per\ second.

7 0
2 years ago
Calculate the average speed and average velocity of a complete round-trip in which the outgoing 250 km is covered at 95 km/h fol
ser-zykov [4K]

To solve this problem we will apply the concepts related to the kinematic equations of linear motion. From them we will consider speed as the distance traveled per unit of time. Said unit of time will be cleared to find the total time taken to travel the given distance. Later with the calculated average times and distances, we will obtain the average speed.

PART A)

The time taken to travel a distance of 250km with a speed of 95km/h is

t = \frac{d}{v}

t = \frac{250km}{95km/h}

t = 2.63h

Time taken for the lunch is

t = 1h

The time taken travel a distance of 250km with a speed of 55km/h

t = \frac{d}{v}

t = \frac{250}{55}

t = 4.54h

The total time taken is

t = t_{outgoing}+t_{lunch}}t_{return}

t = 2.63+1+4.54

t = 8.17h

The average speed is the ratio of total distance and total time

v = \frac{250+250}{8.17}

v = 61.15km/h

PART B)

As the displacement is zero the average velocity is zero.

5 0
2 years ago
An Object moving at a velocity of 30 m/s slows to a stop in 7 seconds. What was its acceleration
ollegr [7]

Answer:

<h3>The answer is 4.29 m/s²</h3>

Explanation:

The acceleration of an object given it's velocity and time taken acting on it can be found by using the formula

acceleration =  \frac{velocity}{time}  \\

From the question

velocity = 30 m/s

time = 7 s

We have

acceleration =  \frac{30}{7}  \\  = 4.285714...

We have the final answer as

<h3>4.29 m/s²</h3>

Hope this helps you

7 0
2 years ago
An archer draws her bow and stores 34.8 J of elastic potential energy in the bow. She releases the 63 g arrow, giving it an init
elena-14-01-66 [18.8K]

Answer:

Approximately 71\%.

Explanation:

The formula for the kinetic energy \rm KE of an object is:

\displaystyle \mathrm{KE} = \frac{1}{2}\, m \cdot v^2,

where

  • m is the mass of that object, and
  • v is the speed of that object.

Important: Joule (\rm J) is the standard unit for energy. The formula for \rm KE requires two inputs: mass and speed. The standard unit of mass is \rm kg while the standard unit for speed is \rm m \cdot s^{-1}. If both inputs are in standard units, then the output (kinetic energy) will also be in the standard unit (that is: joules,

Convert the unit of the arrow's mass to standard unit:

m = 63\; \rm g = 0.063\; \rm kg.

Initial \rm KE of this arrow:

\begin{aligned}\mathrm{KE} &= \frac{1}{2} \, m \cdot v^2 \\ &= \frac{1}{2}\times 0.063\; \rm kg \times \left(\rm 28 \; m \cdot s^{-1}\right)^2 \\ &\approx 24.696\; \rm J\end{aligned}.

That's the same as the energy output of this bow. Hence, the efficiency of energy transfer will be:

\displaystyle \frac{24.696\; \rm J}{34.8\; \rm J} \times 100\% \approx 71\%.

8 0
2 years ago
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