A bullet is fired through a board 10 cm thick in such a way that the bullet's line of motion is perpendicular to the face of hte board. if the initial sped of the bullet is 400 m/s and it emerges from the other side of hte board with a speed of 300 m/s, discover (a) the acceleration of the bullet as it passes through the board (b) the total time the bullet is in contact with the board.