Question

newtons third law of motion states that for every action, there is an equal and opposite reaction. it is also called the law of action-reaction.

an action force is a force acting in a specific direction. a reaction force is a force acting in the opposite direction as another force.

action-reaction forces act in pairs and are equal and opposite.

this weightlifter lifts weights above his head. the action is the weightlifter pushing up on the weights and the reaction is the weights pushing down on the weightlifter.

choose the correct answer.
a weightlifter lifts weights above his head. what is the action force?
the weights push the weightlifter downwards.
the weightlifter pushes up on the weights.
the weightlifter pushes down on the weights.

Explanation:

To determine the action force when a weightlifter lifts weights, we refer to Newton's Third Law (action - reaction pairs) and the provided text. The text states that the action is the weightlifter pushing up on the weights (with the reaction being the weights pushing down on the weightlifter). Let's analyze each option:

• Option 1 ("The weights push the weightlifter downwards") describes the reaction force, not the action force.
• Option 2 ("The weightlifter pushes up on the weights") matches the definition of the action force as per the given text and Newton's Third Law (the weightlifter initiates the upward push on the weights).
• Option 3 ("The weightlifter pushes down on the weights") is incorrect because the weightlifter is lifting the weights, so the force on the weights is upward, not downward.

Answer:

The weightlifter pushes up on the weights.