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3 years ago

15

you arrive in hampton 45 seconds after you left York college which is 50 feet away how fast did you travel

1 answer:

Nimfa-mama [501]3 years ago

4 0

.9 feet per second, because 45 divided by 50 equals .9

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The best solution for the problem of pollution by man-made technologies A. cannot involve anyone who is not a technology expert

Ber [7]

Answer:

is likely to come from collaborative efforts by technology experts and experts on pollution.

Explanation:

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3 years ago

If I have a 78c and I fail a test that’s worth 15% of my grade what would it drop to ?

koban [17]

Depends on the grade of the test. But for the most part if it’s below a 78, it’ll drop, If it’s above it’ll raise. It shouldn’t drop or raise it more than 3 point/percent.

8 0

2 years ago

The radioactive isotope of lead, Pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.

Marina86 [1]

Answer:

Therefore it will take 7.66 hours for 80% of the lead decay.

Explanation:

The differential equation for decay is

$\frac{dA}{dt}= kA$

$\Rightarrow \frac{dA}{A}=kdt$

Integrating both sides

ln A= kt+c₁

$\Rightarrow A= e^{kt+c_1}$

$\Rightarrow A=Ce^{kt}$ [ $e^{c_1}=C$ ]

The initial condition is A(0)= A₀,

$\therefore A_0=Ce^{0.k}$

$\Rightarrow C=A_0$

$\therefore A=A_0e^{kt}$ .........(1)

Given that the $Pb_{209}$ has half life of 3.3 hours.

For half life $A=\frac12 A_0$ putting this in equation (1)

$\frac12A_0=A_0e^{k\times3.3}$

$\Rightarrow ln(\frac12)= 3.3k$ [taking ln both sides, $ln \ e^a=a$ ]

$\Rightarrow k=\frac{ln \frac12}{3.3}$

⇒k= - 0.21

Now A₀= 1 gram, 80%=0.8

and A= (1-0.8)A₀ = (0.2×1) gram = 0.2 gram

Now putting the value of k,A and A₀in the equation (1)

$\therefore 0.2=1e^{(-0.21)\times t}$

$\Rightarrow e^{-0.21t}=0.2$

$\Rightarrow -0.21t= ln(0. 2)$

$\Rightarrow t= \frac{ln (0.2)}{-0.21}$

⇒ t≈7.66

Therefore it will take 7.66 hours for 80% of the lead decay.

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3 years ago

How many atoms in the pictured molecule can form hydrogen bonds with water molecules anatomy?

garri49 [273]

55..............................

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2 years ago

Please help asap :)))))

deff fn [24]

Answer:

um i dont know anything about music sorry

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2 years ago