A swift blow with the hand can break a pine board. As the hand hits the board, the kinetic energy of the hand is transformed into elastic potential energy of the bending board; if the board bends far enough, it breaks. Applying a force to the center of a particular pine board deflects the center of the board by a distance that increases in proportion to the force. Ultimately the board breaks at an applied force of 860N and a deflection of 1.6cm .
To break the board with a blow from the hand, how fast must the hand be moving? Use 0.50kg for the mass of the hand.