<span>In order to calculate an average, we should sum all numbers and divide them by quantity.
Let’s work with qualifications first. Let’s say you got a 10 in 1 exam, then an 8 in 2 exams and a 4 in 2 exams. Your average will be:
= (10*1+8*2+4*2) / 5 = 6.8
If 6 is the minimum, you will pass.
There is another way to calculate this average: applying distributive property.
= 10*1/5+8*2/5+4*2/5 = 6.8
Remember you can convert the fractions into equivalent fractions: 1/5 = 20/100; 2/5 = 40/100
= 10*20/100+8*20/100+4*20/100 = 6.8
We actually don’t have the number of atoms of each mass… we have the percentage instead! So we need to learn this last method for atoms.
Let’s go back to our atoms problem:
73.71 % of atoms have a mass of 27.98 u
14.93 % of atoms have a mass of 28.98 u
11.36 % of atoms have a mass of 29.97 u
So let’s put that in the formula:
Average mass = 27.98 u*73.71 /100 + 28.98 u*14.93 /100 + 29.97u*11.36 /100
So what you have to know is that a percentage can be converted into a fraction, and you should work that fraction in order to find the average. We can make the calculus shorter putting 100 as the common denominator:
Average mass = (27.98 u*73.71 + 28.98 u*14.93 + 29.97u*11.36)/100
So actually we are taking the percentage as if it was the quantity, and 100 as if it was the total (the total of all percentages is always 100). Maybe we don’t have 100 atoms, but it will be the same proportion anyway, whatever number we have! And here it is the result:
Average mass = 28,36u
</span>
Answer:
I. Models are always wrong unless they are proved by a theory. TRUE
II. Elements, such as lead, are made of tiny particles that mostly consist of open space. FALSE
III. The air you breathe is an example of a heterogeneous mixture. FALSE
IV. An isotope of silver-108 has 61 neutrons. TRUE
Explanation:
I. All models are wrong because in order for them to be applied to reality, certain aspects that do not fit the theory must be considered.
II. All elements are made by atoms.
III. The air is an example of a homogeneous mixture of different gases. IA homogeneous system is that material system that has the same intensive properties in any part of that system. One way to check it is by viewing it. If the different parts that make it up cannot be distinguished, it will be homogeneous.
IV. Atomic number of Silver is 47. So if its mass number is 108, it has 61 neutrons and 47 protons
Answer:
1.526 m
Explanation:
The motion sensor sends sound waves in air which travels at a speed of 343 m per second at 20 degree. If d be the distance of the reflecting object
total distance travelled = 2d
Time taken t = 8.9 x 10⁻³ s
velocity v = 2d / t
343 = 2 d / (8.9 x 10⁻³)
d = 1.526 m
The eagle gained 882 J of gravitational potential energy.
A system of millions or billions of stars together with gas and dust, held together by gravitational attraction