According to Newton's second law, the resultant of the forces acting on the box is equal to the product between its mass and its acceleration:
(1)
we are only concerned about the horizontal direction, so there are only two forces acting on the box in this direction:
- the horizontal component of the force exerted by the rope, which is equal to
- the frictional force, acting in the opposite direction, which is equal to
By applying Newton's law (1), we can calculate the acceleration of the box:
Today, we know that the continents rest on massive slabs of rock called tectonic plates. The plates are always moving and interacting in a process called plate tectonics. The continents are still moving today. Some of the most dynamic sites of tectonic activity are seafloor spreading zones and giant rift valleys.
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 and working shown on photo, final answer for number electrons=2.5*10^17 electrons