Answer:
amusement parks. Each day, we flock by the millions to the nearest park, paying a sizable hunk of money to wait in long lines for a short 60-second ride on our favorite roller coaster. The thought prompts one to consider what is it about a roller coaster ride that provides such widespread excitement among so many of us and such dreadful fear in the rest? Is our excitement about coasters due to their high speeds? Absolutely not! In fact, it would be foolish to spend so much time and money to ride a selection of roller coasters if it were for reasons of speed. It is more than likely that most of us sustain higher speeds on our ride along the interstate highway on the way to the amusement park than we do once we enter the park. The thrill of roller coasters is not due to their speed, but rather due to their accelerations and to the feelings of weightlessness and weightiness that they produce. Roller coasters thrill us because of their ability to accelerate us downward one moment and upwards the next; leftwards one moment and rightwards the next. Roller coasters are about acceleration; that's what makes them thrilling. And in this part of Lesson 2, we will focus on the centripetal acceleration experienced by riders within the circular-shaped sections of a roller coaster track. These sections include the clothoid loops (that we will approximate as a circle), the sharp 180-degree banked turns, and the small dips and hills found along otherwise straight sections of the track.
The answer would be periods 6-7 :)
There is a shortcut trick while doing such fill in the blanks of nuclear reactions of hydrogen and helium
Let a,b,care elements of set N

Now
for our question
Hence b=4-3+1=1+1=2
So
The missing place should b e deuterium of heavy water
In nuclear reactions energy is released so it's mentioned on product side not reactant side
At room temperature, water is liquid in form. For helium, it is gas because it is the second lightest element in nature. So, you would expect the density of Helium to be much less than 1 g/cm³. Because gas is very light and occupies a lot of space, the density would result to a very small number.
c. physical change
Explanation:
The separation of ink into its different pigments during chromatography is a physical change.
Ink is a mixture of many different pigments.
During chromatography, a mixture is separated based on the relative migration of constituents of mixture over an adsorbent.
- Separation techniques are used to celebrate mixtures based on their physical properties.
- During a physical change only the physical properties of matter like their form and state is changed.
- The process is easily reversible and no new kinds of matter are formed.
learn more:
Physical property brainly.com/question/10972073
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