Homework+..+March+13+2010


 * Question** **–** How is effort force affected when applied closer to the fulcrum?


 * Hypothesis** – It Make easier sometimes and harder sometimes so its about the fulcrum and the load.

//Example: The amount of water in the solution is the controlled variable.// 2. The larger end of the meter stick (the 100-cm end) will be for the effort force. 3. Set up your lever like a meter stick with no weights, and the fulcrum close to the middle so the lever acts like a see-saw, balanced in the middle. 4. Put a load of 50 g at the LOAD END of the lever. Put the load as close as possible to the end of the lever. Be careful that the fulcrum stays in place. 5. Apply a force by pushing the Force Sensor down on the FORCE END of the lever. Add **//just//** enough to lift the load. 6. Record the newtons you need to lift the load. (I've done this one as an example below). 7. Repeat steps 4- 6 changing the Effort Force Distance. 8. Record the data in the data table.
 * Variables** –
 * Independent Variable**- The fulcrum//.//
 * Dependent Variable**- The load.
 * Controlled Variable**- The effort force.
 * Procedure** – 1. The smaller end of the meter stick will be for the load force. (The 0cm end). This means that the load you are trying to lift should be at this end.

**__Data Collection and Processing__**
 * Raw Data Table** –

Fulcrum At (cm) || Load at End of Ruler (g) || Load distance (cm) (from fulcrum to load) || Effort Force needed (newtons) || Effort Force Distance (cm) || 50 || 100 || 49 || 1.0 || 49 || 50 || 100 || 49 || .9 || 49 || 50 || 100 || 49 || 1.3 || 40 || 50 || 100 || 49 || 1.7 || 30 ||

Try these other fulcrum placements and find several effort placements that will work.

Fulcrum At (cm) || Load at End of Ruler (g) || Load distance (cm) (from fulcrum to load) || Effort Force needed (newtons) || Effort Force Distance (cm) || 40 || 100 || 40 || .4 || 60 || 40 || 100 || 40 || .4 || 55 || 40 || 100 || 40 || .5 || 50 || 40 || 100 || 40 || .7 || 45 || 30 || 100 || 30 || >1 || 30 || 30 || 100 || 30 || 1.3 || 20 || 30 || 100 || 30 || 1.0 || 15 ||

The Processed Data is different from the Raw Data in that the raw data are simple results of the experiment. Once the data has been processed, it gains meaning. Determine the best way to display your results so that they are clear and easy to understand. This could be with a line graph, bar graph, pie chart, scatter plot, or even a narrative paragraph. //Example: In the lab the penny always held more drops of plain water than of the water and vinegar solution. Since surface tension is the force responsible for a liquid forming into a dome and remaining on a solid surface, it is easy to see that the addition of vinegar did change the surface tension of water. With vinegar added to it, the water does not form and hold the dome shape as well as it does when the water is pure. So the surface tension is decreased when the vinegar is added.//
 * Presentation** **of Processed Data**–

**__Conclusion & Evaluation__** //Example: My hypothesis is correct in that the addition of an acid – vinegar – did change the surface tension of water. This was tested by counting how many drops (of either water or the water and vinegar solution) a penny would hold before it overflowed the edge. Surface tension is what keeps the drops of liquid on the penny and what causes it to form a dome on top of the penny. The penny was able to hold more drops of water than of the water and vinegar solution in all three trials.//
 * Conclusion** – The conclusion is a paragraph in which you get a chance to discuss the results of your experiment and show what you learned. Start by stating whether your data seems to support or refute your hypothesis. Make sure to talk about your data and give support for your conclusions.
 * Limitations of Experimental Design** – In the Limitations of Experimental Design section, you would discusses how well __your experimental design__ helped answer the question in your investigation. Here you explain what worked well (and why) and what did not work well (and why). This is also a section in which outlier points could be discussed (if there were any outlier points) as well as possible reasons for those outlier points.

//Example: In a future investigation, it might be interesting to see if the surface tension of the water and vinegar solution continues to be reduced as more vinegar is added to it.//
 * Suggestions for Improvement** - this paragraph is used to give suggestions on how to improve your experiment. Look at the above section under “what did not work” and explain what might make it better.