Which of the following describes an action-reaction pair? a. you push up on a barbell, and the barbell pushes you down. b. the sun pulls on earth, and earth pulls on the moon c. a man pushes a car forward, and the car pulls the man forward. d. you push down on a desk, and the desk pushes down on the ground.

A. you push up on a barbell, and the barbell pushes you down

Explanation:

As per Newton's third law of motion, every action has an equal and opposite reaction. The point of action and reactionary force are same. If you analyze the options given only first option fulfills this condition.

As you push the barbell up, that means action is being done on the barbell using your hand and barbell pushes you down which means that the reaction force is acting on the same point.

In other options the action is done on one object and the other force is not acting on the same object but some other object.

1/0.14nm = 10^10/1.4 a lot

see earlier answer