Answer:
C
Explanation:
Since the net force is changing, and not the speed, it is C
Hope this helped!
Answer:
We obtain the average velocity instead of the instantaneus velocity.
Explanation:
The problem with calculating speed in this way is that an average speed is being calculated and not an instantaneous speed at a given point.

To calculate the instantaneous speed, a very small space interval must be measured at a given time.
Answer:
it is accepted all over the world
it is more reliable than other kinds of measuring system
the middle part in the center of the diagram. the nucleus is always in the center.