• what is the reaction of normal force in﻿ second statement?

• I don't understand the 2nd statement is false. If you exercise 700N force on the ground (2nd picture) wouldn't that be the same as saying you exercise 700N on the Earth in the 3rd picture. It feels more like﻿ you're juggling with words then you're referring to other forces. I probably don't get it.

• also, maybe the way it is drawn is confusing you,

normal force: (also called contact force), is force perpendicular to the plane an object is on, so technically it should start at the contact point between the egg and the ground (plane).

for simplicity, the vector moved from the ground to the﻿ centre of mass of an object

• the reaction force vector of the normal force would have its tail starting at the contact point and pointing in the opposite direction with the same magnitude..

not a very good explanation, but its quite simple when you think about it, the normal force has its own reaction force, and the force of gravity pulling down also has its own﻿ reaction force BUT the force of gravity and the normal force themselves are NOT action/reaction pairs.

• but isn't the earth﻿ and the egg different bodys? so the third law still hold

• Sal, we would appreciate further clarification on﻿ the second statement.

• To the second statement: as the earth and you are in contact with each other the reaction force that acts on the earth causes the normal﻿ force on the one standing on earth. Isn't it?

• To the second statement:As﻿ the earth and

• more quizzes! :D﻿ people learn best from attempting it and getting it wrong and seeing corrections rather then just being fed information

• Interestingly, while the earth is applying a normal force of 700N upwards to Sal, Sal's feet are applying an equal an opposite force downwards on the earth. Sal﻿ is keeping the earth from flying off into space! (Or, well, at least from flying off in the wrong direction.) Thank you Sal!