Jiujiang mingjue photography

(1) The vertical falling of building wall blocks is regarded as free falling motion h= 12gt2,

The falling time of the solution t=7s.

Escape time t' = 7-0.2 = 6.8s.

The speed for ground personnel to escape from buildings to safe areas should be at least v1= s't' =1006.8 =14.7m/s.

(2) The velocity of falling body before landing V2 = GT = 70m/s

The momentum theorem (mg-F)△t=0-mv2 is used in the landing process.

The average force f of falling objects on the ground is F=5.64× 106N N.

(3) What is the time difference between the arrival of P-wave and S-wave? svs-svp=△t0

Replace: s3 100-s9 100=5.

The distance between the observation recorder and the source is s=23.5km.

A:

(1) Ground personnel must run at a speed of at least 14.7m/s to escape from the building to a safe area.

(2) The average force produced by falling objects on the ground is 5.64×106 n. 。

(3) The distance S between the observer and the source is 23.5km. ..