Which statement correctly describes the motion on which an Earth time interval is based?

1 answer:

4 0

The smswer is b because if there is no day there will be no month so mo year too as it takes the earth to spin 24 hours around so 24 hours is a day.

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An athlete runs 200 m by running 100 m in a straight line and then turning around and running 100m back to the start point.

siniylev [52]

Answer:

Explanation:

The athlete ran a total distance of zero because they ran 100m forward then turned around so they went back to their starting position

6 0

3 years ago

Atom X contains seven protons and seven neutrons. atom Z contains seven protons and eight neutrons. which of the following state

stiks02 [169]

Answer:

The correct answer is option A: they are isotopes.

Explanation:

From atom X we know that the number of protons is 7 and the number of neutrons is 7 and from atom Z we know that the number of protons is 7 and the number of neutrons is 8.

Since the number of protons of atom X and atom Z is the same, we have that atom X and atom Z is the same element. The difference in the number of neutrons tells us that atom X and atom Z are isotopes. Remember that an isotope is one element that has atoms with different numbers of neutrons.

The mass number is given by:

$A = p + n$

Where <em>n</em> is the number of neutrons and <em>p </em>is the number of protons.

For atom X and atom Z we have:

$A_{x} = 7 + 7 = 14$

$A_{z} = 7 + 8 = 15$

Hence, they have a different mass number.

We know that the element with 7 protons is nitrogen. The first isotope is $^{14}_{7}N$ and the second isotope is $^{15}_{7}N$ . Both isotopes are stables (they are not radioactive).