A) Estimate the force with which a karate master strikes a board if the hand's speed at time of impact is 13.7 m/s , decreasing to 0.832 m/s during a constant time of 0.00119 s with the board. The mass of coordinated hand and arm is 1.15 kg .
B) Estimate the shear stress if this force is ex- erted on a 0.412 cm -thick pine board that is 13.7 cm wide.