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If there is friction on this problem then the first box would also experience a reduction in velocity making this a calculus problem. You cannot calculate the frictional force without more information. The second question implies that the third question should be solved by using forces, but the coefficient of friction is missing. Work-energy is not possible.

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Good Afternoon,

     This is designed as a problem to compliment the Regents and Honors programs of study with this website (hence its location in the Regents and Honors folder), in which the coefficient of friction for wood on wood is a given and is designed to be looked up in a reference table (see link below).  And yes, the first box would experience friction, however, based on the problem statement, you know the velocity of the first block as it contacts the second block, therefore there's no need to calculate a reduction in velocity prior to impact.  Then, following the impact, and knowing the coefficient of kinetic friction of wood on wood, you can solve for the horizontal launch velocity using Newton's 2nd Law, at which point this becomes a projectile problem.

Links to reference table with friction information: http://www.aplusphysics.com/courses/honors/dynamics/friction.html

 

I would agree, however, that if you didn't know the coefficient of friction, you'd be stuck.

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