An old lady sits on and pushes down on a park bench. what is the reaction force? a. the bench pushes up on her. b. the earth pulls down on her. c. the bench pushes down on her. d. the earth pushes up on her.
me

Explanation:

The given situation is

According to this situation, the old lady pushes down the surgace of the park bench.

We are being asked about the reaction force. According to Newton's third law  "every action has an equal and opposite reaction", which referst to forces, if we apply a force, there will be an equal and opposite force.

So, in this case, if she is pushing down on a bench, then the bench will push up in return with an equal but force.

Therefore, the right answer here is A. The bench pushes up on her, because she's pushing it down.

diagram is missing, but i will try to explain your doubt.

answer:

amplitude is the maximum displacement or distance moved on a point of a vibrating body or wave measured from its equilibrium position.it is equal to half the length of vibration path.

hypothesising or postulating