$($a$)$ The compression stage typically lasts a few times longer than the time required for

the impacting body to fall down a distance equal to its own diameter. Calculate the duration of the compression stage for R $=10$ m and R $=1$ km meteoroids that impact Earth at v $=15$ km s$-1$

$($b$)$ Estimate the pressure involved in these collisions, assuming the meteoroids are stony bodies with density $=3$ g cm$-3.$