Newton's Third Law: Solving the Man & Sled Puzzle

[brewAP2010]

Homework Statement

If a man pulls forward on a sled, and the sled pulls backward on the man with an equal amount of force, how can the man and sled move at all?

Homework Equations

The Attempt at a Solution

 

[PhanthomJay]

Since the sled will move, you should think about what Newton's 2nd law says compared to his third law. What are your thoughts?

 

[ehild]

If a man pulls forward on a sled, and the sled pulls backward on the man with an equal amount of force, how can the man and sled move at all?

It is not only man and sled, but there is also the Earth they interact with.

ehild

 

[harp AP 2010]

He manages to move the sled by digging in his feet with more resistance than the sled can muster from its friction with the ground. If it were done on ice, he would not need to apply much force.