# 1R10.30: Springs in Series and Parallel

Video: Watch this demo

Instructor’s video

Description: This demonstration illustrates the combination of similar springs (same spring constant).
Most students do not predict the right outcomes, as this is counter intuitive for most.

Equipment:

• 2 Sets of weights
• 4 of the same silver springs
• 3 Square rulers
• Tape
• 3 Long poles
• 3 short rods
• 3 S clamps
• 3 Table clamps

Setup Procedure:

1. Setup the rods and clamps as shown in the picture. Make sure top three rods are at the same height.
2. Tape a square ruler to each post. Make sure all three rulers are at the same height.
3. Attach a spring on the left one, a spring on the middle one, and two springs in series on the right one.

Demonstration Procedure:

1. Use the left spring as a reference point for the unstreched spring.
2. Attach a mass to the middle spring (1kg works good). Note how far it is stretched compared to the reference spring.
3. Ask students what they think will happen when you attach a mass to the 2 springs in series.
4. Attach another equal mass to the 2 springs in series. Note that each strings stretches the same, but combined they stretched twice as much as the middle one.
5. Ask students what will happen if attach the same mass to 2 strings in parallel.
6. Take the mass off the right spring. Take the bottom spring off and attach it to the top right pole.
7. Attach the mass to both strings. Note that each spring stretches half as much as the one in the middle, since each effectively “sees” half the weight.
8. When finished, remove the masses from the springs.

22-C3