大象传媒

Stretching springs experiment

There are different ways to investigate the relationship between force and extension for a spring. In this suggested practical activity, it is important to:

  • make and record length accurately
  • measure and observe the effect of force on the extension of springs
  • collect the data required to plot a force-extension graph

Aim of the experiment

To investigate the relationship between force and extension for a spring.

Method

A聽clamp stand holds both a spring and a ruler. The spring has a weight hooked onto the bottom. The clamp is attached to a bench.
  1. Secure a clamp stand to the bench using a G-clamp or a large mass on the base.
  2. Use bosses to attach two clamps to the clamp stand.
  3. Attach the spring to the top clamp, and a ruler to the bottom clamp.
  4. Adjust the ruler so that it is vertical, and with its zero level with the top of the spring.
  5. Measure and record the unloaded length of the spring.
  6. Hang a 100 g slotted mass carrier (weight 0.98 N) from the spring. Measure and record the new length of the spring.
  7. Add a 100 g slotted mass to the carrier. Measure and record the new length of the spring.
  8. Repeat step 7 until you have added a total of 1,000 g.

Results

Record your results in a suitable table

Force (N)Length (mm)Extension (mm)
0 (unloaded)220
0.985230
1.968361
.........
Force (N)0 (unloaded)
Length (mm)22
Extension (mm)0
Force (N)0.98
Length (mm)52
Extension (mm)30
Force (N)1.96
Length (mm)83
Extension (mm)61
Force (N)...
Length (mm)...
Extension (mm)...

Analysis

Force extension graph. Linear section drawn from origin to occupy two-thirds of graph area. Non linear section has an聽increasing gradient.
  1. For each result, calculate the extension: extension = length - unloaded length
  2. Plot a line graph with extension on the vertical axis, and force on the horizontal axis. Draw a suitable line or curve of best fit.
  3. Identify the range of force over which the extension of the spring is directly proportional to the weight hanging from it.

Evaluation

It is important to keep the ruler vertical. Suggest another way to improve the accuracy of the length measurements.

Hazards and control measures

HazardConsequenceControl measures
Equipment falling off tableHeavy objects falling on feet could bruise or fractureUse a G-clamp to secure the stand
Sharp end of spring recoiling if the spring breaks Damage to eyes, cuts to skinWear eye protection, support and gently lower masses whilst loading the spring
Masses falling to floor if the spring failsHeavy objects falling on feet could bruise or fractureGently lower load onto spring and step back
HazardEquipment falling off table
ConsequenceHeavy objects falling on feet could bruise or fracture
Control measuresUse a G-clamp to secure the stand
HazardSharp end of spring recoiling if the spring breaks
ConsequenceDamage to eyes, cuts to skin
Control measuresWear eye protection, support and gently lower masses whilst loading the spring
HazardMasses falling to floor if the spring fails
ConsequenceHeavy objects falling on feet could bruise or fracture
Control measuresGently lower load onto spring and step back