Answer:
The density of the block is 7.4g/ml.
Explanation:
We can determine the volume of the metal block by taking the difference between the volumes measured in the graduated cylinder:

Now, as we know that the average density of an object is calculated dividing its mass by its volume, we can calculate the density ρ of the metal block using the expression:

Finally, it means that the density of the metal block is 7.4g/ml.
From the answers provided, I believe the possible answer would be the last option, silicon, oxygen, and one or more metals. Here's my reasoning: the most abundant mineral group found in the Earth's crust is the silicate group. The silicate materials contain both oxygen and silicon. Silicates are the most common minerals in the rock-formation process, and it has, in fact, been estimated that they make up 75 to 90 percent of the Earth's crust. From this piece of evidence, I can guess that the answer will possibly be D, silicon, oxygen, and one or more metals.
It should also be noted that the additional elements that combine with the silicon-oxygen tetrahedron are involved with the other elements commonly found in the Earth's crust and mantle. They are aluminum, calcium, iron, magnesium, potassium and sodium.
Answer:
The time interval is 
Explanation:
From the question we are told that
The constant acceleration is 
The displacement is
According to the second equation of motion we have that
given that the blade started from rest
which is the initial angular velocity is 0
So
=> 
substituting values
=> 
=> 
The answer is solely based on the length of space between atoms. In gaseous mediums, atoms are generally quite far apart allowing waves to be undisrupted in the process. In solids and liquids, sound waves are trapped/diluted in the relatively close atom distances