The static frictional force is greater than the kinetic frictional force, so the static frictional force is greater than 1200 N.
They can't hear an echo in small room because in it the sound can't be reflected back. For an echo of a sound to be heard,the minimum distance between the source of sound and the walls of the roomshould be 17.2 m. Obviously,in asmall room echoes cannot beheard.
6 is b. part B on 6 is a. 7 is a. partB ON 7 b