A vertical spring with k = 100 N/m is stretched by x = 0.20 m. What is the force in the spring at that displacement?

A vertical spring with k = 100 N/m is stretched by x = 0.20 m. What is the force in the spring at that displacement?

• A. 18 N
• B. 20 N
• C. 22 N
• D. 24 N

Answer: (B)

Hooke’s law tells us the spring force equals kx. With a spring constant of 100 N/m and an extension of 0.20 m, the force is F = 100 × 0.20 = 20 N. This is the restoring force the spring exerts, directed opposite to the stretch. In a vertical setup, gravity affects the net force on the mass, but the spring’s own force at this displacement is 20 N.

Hooke’s law tells us the spring force equals kx. With a spring constant of 100 N/m and an extension of 0.20 m, the force is F = 100 × 0.20 = 20 N. This is the restoring force the spring exerts, directed opposite to the stretch. In a vertical setup, gravity affects the net force on the mass, but the spring’s own force at this displacement is 20 N.