vasu

a bullet is fired into a trunk of a tree losses1/4 kinetic energy in travelling distance of 5cm .before stopping it travels a further distance of ....

Actually you have to use 4r=/3.a for volume then you get 1095.8 kg/m3 for one atom. and one unit cell has 4 cation (cs+) and 1 anion (cl-) and you have multiply 4x1x1095.8 = 4380 kg/m3.