a bullet traveling horzontally at a speed of 350m/s hits board perpendicular to its surface passes through n emerges on the other side at a speed fo 210m/s. if the board is 4.00cm thick, how long does the bullet take to pass through it.

Answer 1

Divide the width of the board (0.040 m) by the average speed of the bullet going through (280 m/s). This will be an approximate answer.

If the speed of the bullet varies linearly with distance, it is probably best to use an average speed Vav that is given by
1/Vav = 1/350 + 1/210