Practical - the effect of forces on springs - Materials under stress - GCSE Physics (Single Science) Revision - OCR 21st Century

Suggested practical - Investigate the effect of forces on springs

There are different ways to investigate the relationship between force and extension for a spring. In this required 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 relationshhip between force and extension for a spring.

Method

A 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.

Secure a clamp stand to the bench using a G-clamp or a large mass on the base.
Use bosses to attach two clamps to the clamp stand.
Attach the spring to the top clamp, and a ruler to the bottom clamp.
Adjust the ruler so that it is vertical, and with its zero level with the top of the spring.
Measure and record the unloaded length of the spring.
Hang a 100 g slotted mass carrier (weight 1.0 N) from the spring. Measure and record the new length of the spring.
Add a 100 g slotted mass to the carrier. Measure and record the new length of the spring.
Repeat step 7 until you have added a total of 1,000 g.

Results

Record your results in a suitable table.

Force in N	Length in mm	Extension in mm
0 (unloaded)	22	0
1.0	52	30
2.0	83	61

Force in N	0 (unloaded)
Length in mm	22
Extension in mm	0

Force in N	1.0
Length in mm	52
Extension in mm	30

Force in N	2.0
Length in mm	83
Extension in mm	61

Analysis

Force extension graph. Linear section drawn from origin to occupy two-thirds of graph area. Non linear section has an increasing gradient.

For each result, calculate the extension: extension = length - unloaded length.
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.
Identify the range of force over which the extension of the spring is directly proportional to the weight hanging from it.
Calculate the work done in stretching the spring to its elastic limit.
Find out how much energy is stored in the spring when it is stretched to its elastic limit.

Evaluation

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

Hazards and control measures

Hazard	Consequence	Control measures
Equipment falling off table	Heavy objects falling on feet - bruise/fracture	Use a G-clamp to secure the stand
Sharp end of spring recoiling if the spring breaks	Damage to eyes and cuts to skin	Wear eye protection, support and gently lower masses whilst loading the spring
Masses falling to floor if the spring fails	Heavy objects falling on feet - bruise/fracture	Gently lower load onto spring and step back

Hazard	Equipment falling off table
Consequence	Heavy objects falling on feet - bruise/fracture
Control measures	Use a G-clamp to secure the stand

Hazard	Sharp end of spring recoiling if the spring breaks
Consequence	Damage to eyes and cuts to skin
Control measures	Wear eye protection, support and gently lower masses whilst loading the spring

Hazard	Masses falling to floor if the spring fails
Consequence	Heavy objects falling on feet - bruise/fracture
Control measures	Gently lower load onto spring and step back

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Materials under stressPractical - the effect of forces on springs