1. The problem statement, all variables and given/known data A 14.0 kg block is dragged over a rough, horizontal surface by a 78.0 N force acting at 20.0° above the horizontal. The block is displaced 5.00 m, and the coefficient of kinetic friction is 0.300. (a) What is increase in internal energy of the block-surface system due to friction? (b) Find the total change in the block's kinetic energy. 2. Relevant equations (a) Fk=(coefficient of kinetic friction)(mass)(gravity) Change in energy=(Fk)(displacement) (b) Change in K= Work of other forces - Change in energy 3. The attempt at a solution (a)Fk=(coefficient of kinetic friction)(mass)(gravity)=(.3)(14)(9.8)=41.16 Change in energy=(Fk)(displacement)=41.16(5)=205.8J (b)Change in K= Work of other forces - Change in energy = (78.0)(5)(cos20) = 366.5 - 205.8=160.7J however, these answers are wrong...??? Suggestions??