I find what your doing very interesting, but for the two data points that you put on the end it is irrelevant because with connecting those two points with average rates of change. The only way to make sure its still linear would be to add more points and see that the general trend is linear, not just two points that happen to match the slope of your linear constant.
Forget the legos, only look at the ball attracted to the magnet - very different from a string. I measured the rpm by recording the experiment on a video camera at 30 frames/second. I find the rotation where the ball separates from the magnet, then I count the number of frames it takes for it to rotate once after that by stepping frame by frame. This gives me the time in seconds it takes to rotate once and I can calculate RPM from that. Based on RPM and R I can calculate velocity.
Okay, I'll help you figure this out.Say the centre distance between the magnet and the ball is r, the angular velocity w, mass of the ball m, the centripetal force between them is mrw^2. The ball pulls apart at a constant force, which requires constant angular velocity since the separation between ball and magnet is the same. Now, a constant angular velocity means velocity is proportional to the radius.
Yes I understood why you are using a magnet.. it takes roughly a constant force to break free so avoiding having to measure the force... but to me leggo looks very much like string.
Anyway that aside..how are you measuring velocity/rpm?
Yes, this is very confusing on how to measure the force/distance relationship. The key is that instead of measuring a variable force by changing the velocity (ball on string method), I keep the force constant with the magnet and steel ball and vary the centripedal force applied to break the magnet and steel ball apart. Don't get your axle wrapped around the non-contact part, it is just another method of measuring the force/distance relationship.
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TheVin300 1 month ago
I find what your doing very interesting, but for the two data points that you put on the end it is irrelevant because with connecting those two points with average rates of change. The only way to make sure its still linear would be to add more points and see that the general trend is linear, not just two points that happen to match the slope of your linear constant.
Very interesting experiment though.
rugby88 2 years ago
Forget the legos, only look at the ball attracted to the magnet - very different from a string. I measured the rpm by recording the experiment on a video camera at 30 frames/second. I find the rotation where the ball separates from the magnet, then I count the number of frames it takes for it to rotate once after that by stepping frame by frame. This gives me the time in seconds it takes to rotate once and I can calculate RPM from that. Based on RPM and R I can calculate velocity.
franklinthu 3 years ago
Okay, I'll help you figure this out.Say the centre distance between the magnet and the ball is r, the angular velocity w, mass of the ball m, the centripetal force between them is mrw^2. The ball pulls apart at a constant force, which requires constant angular velocity since the separation between ball and magnet is the same. Now, a constant angular velocity means velocity is proportional to the radius.
TheVin300 1 month ago
Yes I understood why you are using a magnet.. it takes roughly a constant force to break free so avoiding having to measure the force... but to me leggo looks very much like string.
Anyway that aside..how are you measuring velocity/rpm?
ColinWatters 3 years ago
Unfortunately your experiment appears to measure the "contact centripedal
force" NOT the "non-contact centripedal force" (your definitions). This is
because you vary the length of the spinning lego arm NOT the distance
between ball and magnet.
ColinWatters 3 years ago
Yes, this is very confusing on how to measure the force/distance relationship. The key is that instead of measuring a variable force by changing the velocity (ball on string method), I keep the force constant with the magnet and steel ball and vary the centripedal force applied to break the magnet and steel ball apart. Don't get your axle wrapped around the non-contact part, it is just another method of measuring the force/distance relationship.
franklinthu 3 years ago