WTMA Springs and Elasticity 3 — Questions and Answers
Question 1: A spring has a spring constant of 10 lb/in. How much force is needed to compress it 6 inches?
- 6 lb
- 10 lb
- 60 lb (Correct answer)
- 16 lb
Correct answer: 60 lb
By Hooke's Law, F = k × x = 10 lb/in × 6 in = 60 lb.
Question 2: Which factor does NOT affect a coil spring's stiffness?
- Wire diameter
- Coil diameter
- Number of active coils
- Color of the wire (Correct answer)
Correct answer: Color of the wire
Wire diameter, coil diameter, and number of active coils all affect spring stiffness; wire color has no effect.
Question 3: A bungee cord stretches far more than a steel spring under the same load. This means the bungee cord has a:
- Higher spring constant
- Lower spring constant (Correct answer)
- Greater elastic limit only
- Greater density
Correct answer: Lower spring constant
Greater stretch under the same load means less resistance to deformation, which corresponds to a lower spring constant.
Question 4: When a compressed spring is suddenly released, the stored energy is primarily converted into:
- Heat
- Electrical energy
- Kinetic energy (Correct answer)
- Chemical energy
Correct answer: Kinetic energy
The elastic potential energy stored in a compressed spring converts to kinetic energy as the spring returns to its natural length.
Question 5: Spring A stretches 2 inches under a 10-lb load; Spring B stretches 1 inch under the same 10-lb load. Which spring is stiffer?
- Spring A
- Spring B (Correct answer)
- They are equally stiff
- Cannot be determined
Correct answer: Spring B
Spring B has k = 10 lb/in versus Spring A's k = 5 lb/in, so Spring B is stiffer.
Question 6: What does 'elastic deformation' mean?
- A permanent change in shape
- A temporary change that reverses when force is removed (Correct answer)
- Breaking of the material
- A change in the material's color
Correct answer: A temporary change that reverses when force is removed
Elastic deformation is fully reversible — the material returns to its original shape once the applied force is removed.
Question 7: A coil spring with 20 active coils is replaced by one with 10 active coils (same wire diameter and coil diameter). The new spring is:
- Half as stiff
- Equally stiff
- Twice as stiff (Correct answer)
- Four times as stiff
Correct answer: Twice as stiff
Spring constant is inversely proportional to the number of active coils, so halving the coils doubles the stiffness.
WTMA Springs and Elasticity 3
A spring has a spring constant of 10 lb/in.
How much force is needed to compress it 6 inches?