Answer:
B
Explanation:
Two atoms which are isotopes of one another must have a different number of neutrons.
Isotopes are defined as atoms of the same element which have the same numbers of protons i.e. atomic number remains the same, but has different numbers of neutrons. It is observed that they have same chemical properties due to the same electronic configuration but physical properties differs.
Answer:
The BOD concentration 50 km downstream when the velocity of the river is 15 km/day is 63.5 mg/L
Explanation:
Let the initial concentration of the BOD = C₀
Concentration of BOD at any time or point = C
dC/dt = - KC
∫ dC/C = -k ∫ dt
Integrating the left hand side from C₀ to C and the right hand side from 0 to t
In (C/C₀) = -kt + b (b = constant of integration)
At t = 0, C = C₀
In 1 = 0 + b
b = 0
In (C/C₀) = - kt
(C/C₀) = e⁻ᵏᵗ
C = C₀ e⁻ᵏᵗ
C₀ = 75 mg/L
k = 0.05 /day
C = 75 e⁻⁰•⁰⁵ᵗ
So, we need the BOD concentration 50 km downstream when the velocity of the river is 15 km/day
We calculate how many days it takes the river to reach 50 km downstream
Velocity = (displacement/time)
15 = 50/t
t = 50/15 = 3.3333 days
So, we need the C that corresponds to t = 3.3333 days
C = 75 e⁻⁰•⁰⁵ᵗ
0.05 t = 0.05 × 3.333 = 0.167
C = 75 e⁻⁰•¹⁶⁷
C = 63.5 mg/L
Frequency and wavelength are inversely proportional.
A shorter wavelength implies a higher frequency.
Answer:
Option D
Explanation:
The options for the question are
a) How do galaxies rotate?
b) What is the weather on Neptune?
c) What is the core of Saturn made of?
d) What other solar systems have planets?
Solution
The Hubble space telescope was designed and integrated into the extraterrestrial system in order to capture information about the surrounding universe. If the Keck Observatory has a better observation capacity than the Hubble space telescope then the scientist would be interested to know the surrounding planets in the solar system.
Hence, option D is correct
A rock is dropped from a 100-m-high cliff. How long do the first 50 meters and the second 50 meters take to fall?
(a) The first 50 meters:
h1 = 0.5 x a x t12
50 m = 0.5% x 9.8% x t12
t1 = 3.19 s
50 meter fall time equals 3.19 seconds.
(a) Counting all 100 meters:
h2 = 0.5 x a x t22
100 m = 0.5% x 9.8% x t22
t2 = 4.52 s
Time to fall 50 meters is equal to t2 - t1 = 1.33 s.
<h3>What is meter?</h3>
The Earth's circumference is around 40000 km, according to the original definition of the metre in 1793, which was one ten-millionth of the distance between the equator and the North Pole on a great circle. The metre was redefined in 1799 using a model metre bar (the actual bar used was changed in 1889). The definition of the metre in terms of a certain number of wavelengths of a specific krypton-86 emission line was made in 1960.
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