Which method is ineffective in breaking the security of a physical barrier?

Jamming is a method that interferes with communication signals or electronics, often used in the context of wireless security. However, when it comes to breaking the security of a physical barrier, jamming does not apply. Physical barriers, such as locks, doors, or fences, are structures designed to provide tangible security against unauthorized access. Jamming would not directly affect the integrity of these structures; rather, it impacts communication systems that might be linked to security alarms or monitoring systems.

On the other hand, bending, pulling apart, and breaking involve direct physical force or manipulation of the barrier itself, making them effective methods to compromise physical security. They seek to alter the state of the physical barrier, thereby allowing access. Therefore, jamming is ineffective in physically altering or defeating a barrier's security, which is why it stands out as the correct answer.