RopeLab Quiz 3: Factors of Safety
A quick quiz to test your understanding of the true implication of the term ‘Factor of Safety’.
There are 6 multiple choice questions.
Once you have finished, click on the “View questions” link at the end to see worked answers to each question.
RopeLab Quiz 3: Factors of Safety
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To do this quiz you’ll need to forget about what SF you normally use. Just answer each question.
The scenario assumes a site safety officer (not a rope specialist) walks up, looks at your system and asks what Factor of Safety you think you have. In other words: How many times over could the system support the current load before you expect it to fail?
Hint: go through each element and determine the force at which it may fail. For example, if the weakest element may fail at 9kN and the applied load is 3kN then the Factor of Safety is 3.
Make sure you read the assumptions stated in this image:
Note: all images in this quiz were created with vRigger (see http://www.vrigger.com for details)
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Question 1 of 6
1. Question
1 pointsUse the assumptions in this image for all of the questions in the quiz:
What is the Factor of Safety for the setup shown below?
The 3kN load is supported by a single strand of knotted rope.
Correct
The rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The load is 3kN.
15kN ÷ 3kN = 5
So, the Factor of Safety is 5.
Incorrect
The rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The load is 3kN.
15kN ÷ 3kN = 5
So, the Factor of Safety is 5.

Question 2 of 6
2. Question
1 pointsWhat is the Factor of Safety?
The 3kN load is supported by a double strand of knotted rope. Assume that the load is shared equally by the two ropes.
Correct
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The two ropes are in parallel so, combined, they should give a minimum of 30kN.
The carabiner is rated to 24kN.
The weakest link in the chain is the carabiner (24kN).
The load is 3kN.
24kN ÷ 3kN = 8
So, the Factor of Safety is 8.
Incorrect
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The two ropes are in parallel so, combined, they should give a minimum of 30kN.
The carabiner is rated to 24kN.
The weakest link in the chain is the carabiner (24kN).
The load is 3kN.
24kN ÷ 3kN = 8
So, the Factor of Safety is 8.

Question 3 of 6
3. Question
1 pointsWhat is the Factor of Safety?
The 3kN load is supported by a double strand of knotted rope but tied directly to the load. Assume that the load is shared equally by the two ropes.
Correct
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The two ropes are in parallel so, combined, they should give a minimum of 30kN.
The weakest link in the chain is the pair of ropes (30kN).
The load is 3kN.
30kN ÷ 3kN = 10
So, the Factor of Safety is 10.
Incorrect
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The two ropes are in parallel so, combined, they should give a minimum of 30kN.
The weakest link in the chain is the pair of ropes (30kN).
The load is 3kN.
30kN ÷ 3kN = 10
So, the Factor of Safety is 10.

Question 4 of 6
4. Question
1 pointsCorrect
The internal ‘sling’ angle of the Yhang is less than 120° so tension in the arms of the Yhang will be less than the tension in the single descending strand. Thus there is no need to analyse the Yhang.
The single descending strand of rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The carabiner is rated to 24kN.
The weakest link in the chain is the knotted rope (15kN).
The load is 3kN.
15kN ÷ 3kN = 5
So, the Factor of Safety is 5.
Incorrect
The internal ‘sling’ angle of the Yhang is less than 120° so tension in the arms of the Yhang will be less than the tension in the single descending strand. Thus there is no need to analyse the Yhang.
The single descending strand of rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The carabiner is rated to 24kN.
The weakest link in the chain is the knotted rope (15kN).
The load is 3kN.
15kN ÷ 3kN = 5
So, the Factor of Safety is 5.

Question 5 of 6
5. Question
1 pointsWhat is the Factor of Safety?
The 3kN load is supported by a single strand of knotted rope which runs up through an overhead pulley and back down to a ground anchor.
Correct
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The pulley is rated to 30kN.
The carabiners are rated to 24kN.
The top carabiner supports two strands of rope so it could fail when the tension in each strand reaches 12kN.
The weakest link in the chain is this top carabiner (24kN) when loaded with 12kN applied by the load.
The load is 3kN.
12kN ÷ 3kN = 4
So, the Factor of Safety is 4.
Incorrect
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The pulley is rated to 30kN.
The carabiners are rated to 24kN.
The top carabiner supports two strands of rope so it could fail when the tension in each strand reaches 12kN.
The weakest link in the chain is this top carabiner (24kN) when loaded with 12kN applied by the load.
The load is 3kN.
12kN ÷ 3kN = 4
So, the Factor of Safety is 4.

Question 6 of 6
6. Question
1 pointsWhat is the Factor of Safety?
The 3kN load is supported by a single strand of knotted rope which runs through two overhead pulleys and back down to a ground anchor.
Correct
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The carabiners are rated to 24kN and the pulleys to 30kN.
The internal rope angle at each pulley is 90° which means that the pulley/carabiner/anchor will see 1.41 times the tension in the rope.
The weakest part of the pulley/carabiner/anchor chain is the 24kN carabiner.
24kN ÷ 1.41 = 17kN
So if the rope tension reaches 17kN then the carabiner could fail.
However the knotted rope could fail as low as 15kN and so it is the weakest link in the system.
The load is 3kN.
15kN÷ 3kN = 5
So, the Factor of Safety is 5.
Incorrect
A single rope is rated to 30kN but it is knotted so it could potentially fail as low as 15kN.
The carabiners are rated to 24kN and the pulleys to 30kN.
The internal rope angle at each pulley is 90° which means that the pulley/carabiner/anchor will see 1.41 times the tension in the rope.
The weakest part of the pulley/carabiner/anchor chain is the 24kN carabiner.
24kN ÷ 1.41 = 17kN
So if the rope tension reaches 17kN then the carabiner could fail.
However the knotted rope could fail as low as 15kN and so it is the weakest link in the system.
The load is 3kN.
15kN÷ 3kN = 5
So, the Factor of Safety is 5.
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About The Author
Richard Delaney
Richard Delaney has worked professionally with ropes since 1992 as a multipitch rockclimbing instructor, technical rescue instructor and rope access technician. Understanding and teaching the Physics of Rigging is a core passion of Richard’s, one based on his experience, and his prior professional life as a qualified engineer.