Force and Extension

• Equipment

  Set up the equipment - a spring with a wooden splint as a pointer, ,mass, ruler , and clamp stand with two bosses and two clamps, (like the image) also place a heavy weight on stand to stop it falling over

  
• RP06 - Force and Extension

  1. Set up a weighted stand with a clamp at the top with a metre long ruler and a spring at the end of the clamp. Attach a tape (to mark end of spring).

  2. Measure the initial length of the spring without any weights attached.

  3.Add a 10g mass to the base of the spring and record the length of the spring.

  5. Repeat and continue to add masses, ensuring that the spring doesn't oscillate after each weight has been added.

  6. Calculate the extension of the spring for each mass by subtracting the initial length of the spring from each different length of the spring.

  7. Convert all masses to weights using the equation:

  Weight (N) = mass (kg) x 9.81 (N/kg)

  where 9.81N/kg is the gravitational field strength on Earth.
• RP06 - Force and Extension (Expected Results)

  If the spring obeys Hooke's Law, the graph of force against extension will be linear and pass through the origin. The gradient will be equal to 1 / k, where k is the Spring Constant measured in N/m.
• Method 


  . 1. Read position of pointer on metre ruler, this is unstretched length of spring 2. hang a 1N weight on the spring and read the new position of pointer on metre rule. 3. continue adding 1N weight to spring and reading the position of pointer. 4. Workout extension produced by adding each weight by subtracting the length of unstretched spring from each reading.
• How to find weight of mystery object. 


  measure the extension of the mystery object, e.g. a stone, and read weight from the graph
• The graph: for a spring

  Weight and extension are directly proportional and the graph is linear (a straight line). Graph shows the spring is elastic because if we remove weight extension will return to zero. But, if we add too much weight graph will stop being linear, as we have overstretched the spring = inelastic deformation, we have exceeded the limit of proportionality

  
• Safety: 


  Wear safety goggles to protect eyes in case spring snaps and hits you in the face. Add heavy weight to clamp stand to prevent it tipping over.