how is the bomb constructed to ensure that it does not go off immediately?

Answer 1

There are different ways of doing this.

In nuclear bombs, they usually have an altitude detector that isn't armed until the bomb is dropped. You don't actually want a nuke to hit, you want it to detonate above the ground to do the most damage.

Other types of bombs have pressure sensors, or other apparatus to let the bomb know it has hit a target. Again, these have some kind of fail-safe in place until they are released to keep them from going off.

Other kinds of bombs can be rigged with remote controls, motion sensors, tripwires, etc.

As many bomb-makers who are missing limbs, or have blown themselves to kingdom come will tell you, there is no gaurantee that a bomb won't go off immediately.

Answer 2

If you are referring to an atomic device then:

All of the componets of the device are in place and are active, the issue is that fissible material at standard density can not typically sustain a chain reaction (why nuclear reactors don't explode). The hemi-core of nuclear material are compacted (using conventional explosives) to from a sub-critical mass to critical mass which is capable of sustained chain reaction.

This is also true of fusion (hydrogen) bombs, however at least in the first few generations, the material is compress via a fission device.

Answer 3

Use a timer, set it for 1 second

Answer 4

There is a timer or a delay on the fuse.

Answer 5

what do you mean ? a good explosive should be fairly stable, and only when needed explode.