The mass of an atom comes from the protons and neutrons that is found in the nucleus. The number of protons is the atomic number of an element. To find the number of neutrons, subtract the atomic number from the mass of an atom. For example, sodium’s atomic number is 11. This will tell us that sodium has 11 protons in it. The atomic mass of sodium is 23. So subtract 23 form 11 gives us 12. Therefore, there are 12 neutrons in sodium.
<span>Astronomers are able to determine facts about the composition of these moons by examining the nature of light that is reflected from their surfacy using a method called spectroscopy. This process works because different materials tend to reflect light at different wavelengths So, by observing at which wavelengths a planetary body reflects light, astronomers are able to estimate its composition.</span>
Answer:
The distance travel by block before coming to rest is 0.122 m
Explanation:
Given:
Mass of block
kg
Initial speed of block

Final speed of block

Coefficient of kinetic friction 
Ramp inclined at angle
28.4°
Using conservation of energy,
Work done by frictional force is equal to change in energy,

Where 



m
Therefore, the distance travel by block before coming to rest is 0.122 m
Answer:
I_{total} = 10 M R²
Explanation:
The concept of moment of inertia in rotational motion is equivalent to the concept of inertial mass for linear motion. The moment of inertia is defined
I = ∫ r² dm
For body with high symmetry it is tabulated, in these we can simulate them by a solid disk, with moment of inertia for an axis that stops at its center
I = ½ M R²
As you hear they ask for the moment of energy with respect to an axis parallel to the axis of the disk, we can use the theorem of parallel axes
I =
+ M D²
Where I_{cm} is the moment of inertia of the disk, M is the total mass of the system and D is the distance from the center of mass to the new axis
Let's apply these considerations to our problem
The moment of inertia of the four discs is
I_{cm} = I
I_{cm} = ½ M R²
For distance D, let's use the Pythagorean Theorem. As they indicate that the coins are touched the length of the square is L = 2R, the distance from any spine to the center of the block is
D² = (R² + R²)
D² = R² 2
Let's calculate the moment of inertia of a disk with respect to the axis that passes through the center of the square
I = ½ M R2 + M R² 2
I = 5/2 M R²
This is the moment of inertia of a disc as we have four discs and the moment of inertia is a scalar is additive, so
= 4 I
I_{total} = 4 5/2 M R²
I_{total} = 10 M R²
Answer: harder
Explanation: nothing is impossible, therefore is harder because the absence of light will not ¨reflect¨the colors to the retina of the eyes