Sunday, September 9, 2012

The Pulley Lab


  • In our Pulley Lab, we manipulated force using a simple machine. First, Ms. Tye demonstrated how to lift .1 meters of string with 2 Newtons, without a pulley. Our group was challenged to create our own pulley and once it was finally built, we successfully reached 1.3 Newtons with 20 cm. of string and 0.5 Newtons using 48 cm. of string. Here is an image of the data we graphed, using a bar graph:





  •   We concluded from our graph that the less force you use, the more distance you have to pull. Force and distance relate inversely. As force increases, distance decreases and as distance increases, force decreases. We also recognized that force x distance = area, or 1/2 (force) = 2 (distance). From our post-lab discussion, we discovered this measure of area is energy, measured in Joules (J) and that work is energy transferred by applying a force over a distance and that Work (J) = Force (N) x Distance (m). But no matter what the measure of force and distance is, the energy is always the same.


  • Real World Connection:


    -http://www2.hesston.edu/Physics/Volleyball/paper.htm
    -In volleyball, at the rate the volleyball is hit, you need to absorb the ball and use less force if you want to get it farther and complete the pass. This is clearly demonstrated in the article above.



Monday, September 3, 2012

Mass vs. Force


  • During our first lab experiment, we studied the relationship between the mass of an object and the force needed to hold it in place. To determine this relationship, we hung brass masses of 200 grams, 500 grams, and 1000 grams from a force probe. First, we converted the mass to kilograms and found the force, in Newtons, needed to support these at rest. Later, we repeated this process using an electronic force probe. We graphed our data with the standard equation, y=mx+b Here is an image of our graph from this experiment: 




  • From our graph, we determined the best-fit line and found the slope of the line to be approximately 10. We plugged this into the formula and got y+10x. With a y-intercept of 0, we replaced y and x with force and mass, from the lab. We discovered that 10 N/kg is the gravitational constant, or g, and then concluded that Force= Mass x Gravity or F=mg. Here is an image from the board in class: