Instructions for this Discussion This is a very old physics brain-teaser: A hors

Question

Instructions for this Discussion This is a very old physics brain-teaser: A horse is pulling a wooden sled across the ground. According to Newton's third law of motion, the force of the horse acting on the sled pulling it forward must be equal and opposite to the force of the sled pulling backward on the horse. According to Newton's second law of motion, only net forces cause accelerations. Since the two forces must add to zero by the third law, the acceleration of the horse and sled must also be zero. So how can the sled ever move, much less accelerate? Fi F2 Make an initial posting before replying to other threads. Grading Criteria This assignment is worth 6 points. For full credit, engage in a discussion with at least one of your classmates who posted a different response than you, justifying your answer

Explanation / Answer

Actually the whole thing is is not being taken into account and is being deliberately confused by giving incomplete analysis of horse and wedge.

Wedge analysis : when we consider the motion of the wedge only force acting on the wedge in horizontal direction is the pulling of the horse, therefore it must accelerate according to the second law.

Horse analysis : now the horizontal forces acting on the horse are : 1) the frictional force by the ground (in the forward right direction) 2) the backward pull of the wedge (by the Newton third law).. Obviously the frictional force is greater of the two resulting in the net motion and Acceleration of the system.

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