Question

extra practice activities
1 think about and list three examples in which structures are made purposefully weak.
2 list these and give reasons for your answer.
3 explain what the purpose of each example is.

Explanation:

For each example, the structure is intentionally made weak. In the case of safety glass, it's about injury prevention. For fuses, it's electrical safety based on the principle of \(I^{2}R\) heating. And for emergency exit doors, it's about facilitating quick escape in emergencies. Each example's weakening is purpose - driven for safety or functionality in specific scenarios.

Answer:

1. Safety glass in car windshields:

• Purpose: When broken, it shatters into small, less - harmful pieces.
• Reason: The weakening (lamination or special tempering) is done to reduce the risk of injury from sharp, large glass fragments in case of an accident.

1. Fuse in an electrical circuit:

• Purpose: To break the circuit when the current is too high.
• Reason: The fuse is made of a material (like a thin wire of a specific metal alloy) that has a lower melting point. When excessive current flows (heating it due to \(I^{2}R\) heating, where \(I\) is current and \(R\) is resistance), it melts (weakens the connection) to protect electrical appliances and prevent fires.

1. Emergency exit doors in buildings:

• Purpose: To be easily opened in case of an emergency.
• Reason: They are made with weaker locking mechanisms (compared to regular doors) so that in a fire or other emergency, people can quickly escape. The weakening of the locking structure (e.g., using panic bars instead of complex locks) ensures rapid egress.