Differential Equations     Math 285    Hour Exam 1   Fall, 2011

 

 

 

 

 

 

 

 

 

 

 

 

5.

 

A bullet enters a  10 cm  (0.2 m) wide board at the speed of  250 m/sec and leaves

the board with the speed of  50 m/sec.  How long does it take the bullet to go

through if the resistance is proportional to the speed of the bullet?  (Your answer

may include roots, exponents, logs, etc.)

 

           

 

 

Answer:       t  =   ln 5 / 2000