Question

A bullet traveling horizontally at a speed of 350 m/s hits a board perpendicular to the surface, passes through it, and emerges on the other side at a speed of 210 m/s. if the board is 4.00 cm thick, how long does the bullet take to pass through it? (assume a constant deceleration as the bullet passes through the board.

Answer 1

The average speed of the bullet as it travels through board,

 $v=\frac{350 m/s+210 m/s}{2} =280 m/s$

As the speed of the bullet decreases linearly in the board, therefore the time of the bullet travels through the board is

$t= \frac{distance}{v_{ave} }$

As the board is 4.0 cm ( 0.04 m) thick, therefore

$t= \frac{0.04 m}{280 m/s} =1.43 \times 10^{-4} s$

Thus, the time taken by the bullet to pass the board is $1.43 \times 10^{-4} s$.