Because the moon orbits the earth and when the moon gets in front of the sun it blocks the sunlight and then it becomes night
Answer:
The density of the substance is 3.9 grams per cubic centimeter.
Explanation:
Given mass=27.3 grams
volume=7 cubic centimeter
We need to find the density.
Density of a substance can be calculated by dividing mass of substance by volume of a substance


Hence Density of the substance is
.
A. I’m not positive but I’m pretty sure
Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g