WTMA Springs and Elasticity 2 — Questions and Answers
Question 1: A spring stretches 3 inches when a 15-lb weight is hung from it. How far will it stretch with a 25-lb weight?
- 3 inches
- 5 inches (Correct answer)
- 7 inches
- 25 inches
Correct answer: 5 inches
The spring constant is 15/3 = 5 lb/in, so a 25-lb load stretches it 25/5 = 5 inches.
Question 2: If two identical springs (each with spring constant k) are connected in parallel, what is the combined spring constant?
- k/2
- k
- 2k (Correct answer)
- 4k
Correct answer: 2k
Springs in parallel add their constants directly, so the combined constant is k + k = 2k.
Question 3: A spring is stretched beyond its elastic limit. What happens when the force is removed?
- It returns exactly to its original length
- It stays partially stretched (Correct answer)
- It breaks immediately
- It doubles in length
Correct answer: It stays partially stretched
Once the elastic limit is exceeded, the spring undergoes permanent (plastic) deformation and will not fully recover.
Question 4: Which of the following best describes a spring with a high spring constant?
- It stretches easily under small loads
- It requires large force for small deflection (Correct answer)
- It has many active coils
- It is made of rubber
Correct answer: It requires large force for small deflection
A high spring constant (k) means the spring is stiff — it resists deformation and requires a large force to stretch or compress it a small amount.
Question 5: A mechanic cuts a coil spring in half. What happens to the spring constant of each half?
- It is halved
- It remains unchanged
- It is doubled (Correct answer)
- It is quadrupled
Correct answer: It is doubled
Fewer active coils means less flexibility, so cutting a spring in half doubles its spring constant.
Question 6: A spring scale used to weigh objects operates on which principle?
- Magnetic attraction
- Hooke's Law (Correct answer)
- Pascal's Law
- Newton's Third Law
Correct answer: Hooke's Law
A spring scale uses Hooke's Law — the deflection of the spring is proportional to the applied force (weight).
Question 7: Two identical springs (spring constant k each) are connected end-to-end in series. What is the combined spring constant?
- 2k
- k
- k/2 (Correct answer)
- 4k
Correct answer: k/2
Springs in series have a combined constant of 1/(1/k + 1/k) = k/2, making the assembly more flexible than either spring alone.
WTMA Springs and Elasticity 2
A spring stretches 3 inches when a 15-lb weight is hung from it.
How far will it stretch with a 25-lb weight?