Question

Mountaineering rope should have

• A. High tenacity and high modulus
• B. High elongation, high work of rupture and low modulus
• C. High work of rupture
• D. High tenacity, high modulus and high work of rupture

Hint:

For safety ropes, energy absorption is more important than stiffness. High elongation and low modulus reduce impact forces.

Answer 1

The Correct Option is B

Step 1: Understanding the application.
Mountaineering ropes are used for safety during climbing and must absorb sudden shock loads when a climber falls. Therefore, energy absorption is more important than stiffness.
Step 2: Role of elongation and modulus.
High elongation allows the rope to stretch during a fall, reducing the peak force transmitted to the climber. A low modulus indicates flexibility, which helps in shock absorption.
Step 3: Importance of work of rupture.
High work of rupture means the rope can absorb a large amount of energy before breaking, which is critical for safety in mountaineering.
Step 4: Conclusion.
Thus, mountaineering ropes should have high elongation, high work of rupture, and low modulus.

Answer 2

A mountaineering rope's main job during a fall is to absorb sudden shock energy without transmitting a dangerously high jerk to the climber, so the ideal property combination should favour energy absorption and give over pure stiffness or strength alone. Testing each option against this requirement shows why one stands out.

1. High tenacity and high modulus: High modulus means the rope is stiff and resists stretching. In a fall, a stiff rope stops the climber almost instantly, generating a very high peak force that can cause injury even if the rope itself does not break.
2. High elongation, high work of rupture, low modulus: Low modulus lets the rope stretch considerably under sudden load, spreading the arrest of a fall over a longer time and distance and reducing the peak force on the climber. High work of rupture means the rope can absorb a large amount of energy before it fails, and high elongation is exactly the mechanism that allows that energy to be absorbed gradually.
3. High work of rupture alone: Energy-absorbing capacity is necessary but not sufficient on its own; without also being able to elongate freely, the rope could still arrest the climber too abruptly even if it can eventually absorb a lot of energy.
4. High tenacity, modulus and work of rupture: Adding high modulus back into the mix reintroduces the stiffness problem from option 1 - a high-modulus rope cannot give gradually, so combining it with high work of rupture does not solve the shock-loading issue.

Because the priority in a fall-arrest rope is a gradual, cushioned stop, low modulus and high elongation paired with high energy-absorbing capacity is what actually protects the climber.

Therefore, the correct answer is High elongation, high work of rupture and low modulus.