Physics Lab: Force Table
Goal: to become familiar with force measurements.
Materials and Equipment
Remember that the setup below is a suggestion; any setup which will produce a force table on which you can read the angles of your as-much-as-possible freely swinging weights will work.
- a metal ring (use frictionless ring from kit if you have it)
- nylon thread (must be smooth)
- two half-moon protractors made of clear plastic
- stand (for example, a tall thin box, such as an oatmeal carton, with a flat top)
- standard masses (such as nickels, at 5 gr each)
Assemble the force table as in the diagram. You may need to invert one of the protractors, so be careful when you are reading angles.
- The biggest source of error in this system will be due to friction where the string touches the table surface, so if you can think of a way to minimize friction there, do so. Physics lab force tables use pulleys for each string; any curved surface will help.
- Decide which half is the 0°-180° half of the circle, and which is the 180°-360° portion.
- Tie four nylong strings to the ring. These should be long enough to hang over the edge of your table and allow the attached weights to swing freely.
- Using three or four weights of differing masses, stabilize the ring around the nail, so that it is centered but not touching the nail.
- Record your hypothesis: is the sum of the forces in this situation <0, =0, or >0?
- Record the masses on each string, and the location (0°- 360°) around the table.
- Draw a force vector diagram of your system in equilibrium.
- Sum all the horizontal forces.
- Sum all the vertical forces.
- What do you expect to get for the sum of all the forces in this situation?
- Estimate errors for all measurments and discuss their effect on in your measurements.
- Explain any deviations in experimental data from your calculated data.
- Repeat this procedure for at least 4 different combinations of masses and positions.
Lab Report requirements
Your report should include:
- A description of your equipment and procedure, in enough detail that a reasonably intelligent fellow student could repeat your experiment.
- Your data, arranged in tables or other format so that it is easy to read and relate values.
- Your error estimates for your measurments.
- Your conclusions.
- A description of your equipment and procedures which is sufficiently detailed that I could repeat your experiment myself to check your results.
- Your raw data and calculated data, with explanations of your asusmptions and calculations.
- Your conclusions about acceleration: is it constant?
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