Answer:
Constant or Controlled variables: Same concentration of vinegar solution, same quantity of vinegar, same type of weed etc
Explanation:
In an experiment, certain variables are kept unchanged or constant for both the experimental group and control group in order not to influence the outcome of the experiment. These variables are called CONTROLLED VARIABLES or CONSTANTS.
In the case of this experiment where Lizette is testing the effect of vinegar on weed, the variable that should be kept the same (controlled variables) for the control group of weeds and the sprayed weeds include Same concentration of vinegar solution, Same quantity of vinegar, same type of weed.
Answer:


Explanation:
As the disc is unrolling from the thread then at any moment of the time
We have force equation as

also by torque equation we can say



Now we have



Also from above equation the tension force in the string is


Models show how the atoms in a compound are connected.
For Newton's second law, the resultant of the forces acting on the book is equal to the product between the mass of the book and its acceleration:

(1)
There are only two forces acting on the book:
- its weight, directed downward: mg
- the force exerted by the hand on the book, of 20 N, directed upward
so, equation (1) becomes

from which we can calculate the book's acceleration, a: