When a book that weighs 20 N sits on a table. then the force of gravity from the Earth acts on the book would be 20 N down, therefore the correct option is A.
What is gravity?
It can be defined as the force by which a body attracts another body towards its center as the result of the gravitational pull of one body and another, The gravity varies according to the mass and size of the body for example the force of gravity on the moon is the 1/6th times of the force of gravity on the earth.
When an object is thrown straight up in the absence of air resistance there is no external force acting on it except the gravitational force of the earth which very much reflects the fact that the acceleration due to gravity is constant and is the result of the gravitational pull of the earth which act on the downward direction.
A book that weighs 20 N sits on a table and faces a downward force of 20N acts on the book because the force of gravity from the Earth acts on the book.
Learn more about gravity from here
https://brainly.com/question/4014727
#SPJ5
