Find the efficiency of energy conservation of a staple fired by an elastic band.

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 Harwinder Kalirai  

                                              Physics coursework

Aim

Find the efficiency of energy conservation of a staple fired by an elastic band.

Diagram

Apparatus

2 clamps

2 G- clamps

Elastic string

Staple (2g)

2 Rulers (m)

Weights (N)- 100g masses

Blue-tack

Goggles

String

Theory

Energy conservation: in any process, energy can be transferred but cannot be created or destroyed. There are two types of energies, potential energy (elastic stored energy) and kinetic energy.

Elastic bands have a rest length in which they are in a normal state, having zero elastic energy stored.

When they are stretched they are deprived of their normal state and become storage of elastic energy. Elastic bands have a natural tendency to want to return to there rest state and thus resist being stretched. It is the resistance that provides the elastic energy.

When you release the band it snaps to its original length. This stored elastic energy has been changed to kinetic energy. This provides a force that is strong enough to push the staple into the air, so the staple gained potential energy.

                           

                              Elastic energy                       Potential energy

In this particular experiment stretching the elastic band to find the efficiency of energy transfer of a staple fired by an elastic band.

To find the efficiency of the energy transfer to the staple I will use the equation;

                              Efficiency = mgh   *  100

                                                  Area    

To calculate the potential energy gained by the staple I will use the equation:

                       

                       Potential energy = mg h                 (g = 9.81)

Variables

During the experiment the only factor that I will change will be force applied (by the 100g masses given) to the elastic band. The different weights that I will be using will be: 100g, 200g, 300g, 400g, 500g, 600g, and 700g.

The variables that will stay constant will be:

  1. The height of the clamp from the table to the floor.
  2. The same elastic band will be used.
  3. The same staple will be used.
  4. The same distance from the elastic band to the ceiling (207cm, this will be the maximum height the staple will reach)
  5. The same width of the elastic band while attached to the clamp (5cm)
  6. The same equipment will be used eg clamp and stand, ruler etc.
  7. The length of the string-8cm
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Below is the table, which I will collect my data/results in.

Once I have collected the data I will use it to draw a force-extension graph

as shown below.

If the elastic band obeys Hooke’s law then the results plotted should give us a straight line and then we can find out the elastic energy stored from the area under the graph.

If the elastic band does not obey Hooke’s law then the results plotted will not give us a straight line ...

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