Urgent!Need help with object

Can i know why i can pass through object like rock,tree and etc
is thr any way i can make them stationary and cant pass through?
it seem like the rock will keep moving and i can pass through it

urgent!urgent!

use a collider on your rock

anyone pls help
urgent case~

Erm… sry i am newbie
can i know how can i use a collider?

select an object and go to Component → Physics → and select the appropriate collider.

You should probably read thru the many very well written Unity tutorials.