He was less than an order of magnitude off, which isn''t bad for a high school student. Brett actually built a Cavendish Balance and, using tungsten wire, some high precision lasers and ultra stable platforms loaned by a generous local business, measured G. But the king of projects, the ultimate in AP physics projects, which one person (Brett Hanna I believe was his name) actually did in my class.was to measure the gravitational constant G. Plus, she was an EXTREMELY cute blonde, which I remember most of all. One girl built a bridge out of some kind of polarized plastic, which allowed her to see the stress contours when weights were put on the bridge. For my project, I built a seismograph, which was kind of cool. I took AP physics years ago (1983) and had to do a project. use a longer board, and can also be used to get a sense of how much your results might vary just due to errors in measurement. That gives you some idea of whether you need to make adjustments to the experiment, i.e. Average the values you get and compare that to the individual measurements. angle, surface and ball, several times to get a measure of your accuracy. You can change the ball and/or the surface to better understand what is going on, but you need to keep the measurements seperate. Also the type of ball and type of surface you are rolling it across matters so you want to use the same ball and same surface for a set of measurements at differant angles. Overall the longer the board you are rolling the ball down the less your accuracy in measurement will matter.
You might also want to graph the angle versus the time to see how those vary in relation to one another. does the differance increase or decrease with the elapsed time and angle. Compare the two and try to figure out what is contributing to the differance, i.e. You can try graphing the value you calculate for c versus the angle of the incline and also the value for c versus the time it took to reach the bottom. Also c will vary a bit depending upon the angle of the incline and the variation isn''t all due to the accuracy of your measurement. You can then try to explain that differance. sin(90)=1, but if you measure accurately c will be a bit smaller. a should equal c when the angle is 90 degrees, i.e. So roughly a=c*sin(angle) where c is a constant where c is a constant, but it won''t be exact. If you plot angle versus the acceleration you should roughly approximate a segment of a sine wave. Now you can use trig to calculate the angle of the incline based upon the length of the incline the height of the elevated end. That makes it fairly simple to solve for a. The ball doesn''t start moving until you let go of it so v0 is zero. If you measure distance along the incline with the starting position being zero then s0 is zero. Your position with linear acceleration is s(t)=1/2*a*t^2+v0*t+s0 where s(t) is your position at time t, v0 is the velocity at time 0, s0 is the position at time 0 and a is your acceleration. You can then compare that for differant slopes of the incline. You could roll a ball down an incline plane and measure how long it takes to reach the bottom.
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