P2: Investigating relationship of extension and force

Independent variable

force applied to the free end of the spring

Dependent variable

extension of the spring

Controlled variable

spring constant

Apparatus

• Safety spectacles – one pair for each learner

• Helical spring

• Retort stand, boss-head and clamp

• G-clamp to clamp iron stand to bench

• Mass hanger and slotted masses up to about 500 grams

• Ruler

Method

1. Clamp retort stand with boss head and to bench

2. Attach helical spring and secure it

3. Measure natural length of spring with metre stick

4. Add 100g (1N) mass hanger

5. Measure extended length of the spring.

6. Calculate and record the extension

7. Add a second 100g mass

8. Repeat measurements and record results in a table

9. Plot graph of Force (load)/N) on the x-axis versus extension/cm on the y-axis

Graph

• force/N (y axis)

• extension/cm (x axis)

• line of best fit is straight line through origin up to point

• shows extension of spring is directly proportional to applied force up to limit of proportionality

• beyond it is not proportional and extension increases significantly

Results

as force applied increases, the extension of spring will also increase

Justification

greater stretching force has greater separation of atoms so increases length/ extension

Error

main error is reading stretched length of spring, keep at eye level

Safety

• safety goggles must be worn

• stretched spring could fly off

• retort stand must be secured to bench to prevent it falling