A bullet traveiling horizontally at aspeed of 350 m/s hits a board perpendicular to the surface, passes through it, and emerges on the side at a speed of 210m/s. if the board is 4.oo cm thick, how long does the bullet take to pass through it?

Answer 1

The average speed of the bullet passing through is (1/2)(350 + 210) = 280 m/s. Divide the thickness (4*10^-2 m) by that speed to get the travel time.

Answer 2

.004/280=1/70