A physics student drops a book into a shaft 250m deep,where the average mine temperature is 5 degrees celsius.Show that the sound of the book striking the bottom is heard after 7.82 seconds
Downward motion of the book
t1 =sqrt (2•h/g) = sqrt(2•250/9.8)=
=7.14 s,
Upward motion of the sound (v = 335 m/s)
t2 =h/v = 250/336 =0.74 s.
t = t1 +t2 = 7.14 + 0.74 =7.88 s.