The best answer would be the 4th choice. "They help scientists explain concepts that are difficult to observe, this also covers the first answer which helps the scientist to answer complex questions. A scientific model is not used prove scientific laws as they may not always have all the data to prove so, instead it is used to allow them to explain better concepts revolving around science through research and may also allow them to predict results based on the accumulation of data and analyzing the trend of this resulting information.
Answer:
Ft = 0[N]
Explanation:
To understand this problem we must perform an analysis of forces on the X axis, which coincides with the axis of forces of dogs.
In this way performing a sum of forces on the X-axis we will have (newton's third law):

From this analysis we can see that the resulting or total force is equal to zero, since there is no movement.
Answer:
Explained.
Explanation:
Only the first question has been answered
In a period from left to right the nuclear charge increases and hence nucleus size is compressed. Thus, atomic radius decreases.
In transition elements, electrons in ns^2 orbital remain same which is the outer most orbital having 2 electrons and the electrons are added to (n-1) d orbital. So, outer orbital electron experience almost same nuclear attraction and thus size remains constant.