Question

12 of 20
a ladder leans against a house. what are the action - reaction pairs the ladder was with the wall and then with the ground?
ladder
house (1 point)
ground
$f_{ladder\\ on\\ wall}=-f_{wall\\ on\\ ladder}, - f_{ladder\\ on\\ ground}=f_{ground\\ on\\ ladder}$
$-f_{ladder\\ on\\ wall}=f_{wall\\ on\\ ladder}, - f_{ladder\\ on\\ ground}=f_{ground\\ on\\ ladder}$
$-f_{ladder\\ on\\ wall}=f_{wall\\ on\\ ladder}, f_{ladder\\ on\\ ground}=-f_{ground\\ on\\ ladder}$
$f_{ladder\\ on\\ wall}=-f_{wall\\ on\\ ladder}, f_{ladder\\ on\\ ground}=-f_{ground\\ on\\ ladder}$
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remaining attempts : 3

Explanation:

According to Newton's third - law of motion, for every action, there is an equal and opposite reaction. When the ladder leans against the wall, the force exerted by the ladder on the wall ($F_{ladder\ on\ wall}$) and the force exerted by the wall on the ladder ($F_{wall\ on\ ladder}$) are an action - reaction pair, so $F_{ladder\ on\ wall}=-F_{wall\ on\ ladder}$. Similarly, when the ladder is in contact with the ground, the force exerted by the ladder on the ground ($F_{ladder\ on\ ground}$) and the force exerted by the ground on the ladder ($F_{ground\ on\ ladder}$) are an action - reaction pair, so $F_{ladder\ on\ ground}=-F_{ground\ on\ ladder}$.

Answer:

$F_{ladder\ on\ wall}=-F_{wall\ on\ ladder}, F_{ladder\ on\ ground}=-F_{ground\ on\ ladder}$