F=ma Experiment

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How to see F=ma in action.
Starring: Akash, Jack & Morley

AKASH JAIN (Photographer)
JACK GE (Technical Director)

Tools used- Two iPhone 4s and 1 Blackberry

After we had a quick discussion, we decided to only use a small cart (819g); a few weights with different masses; a pulley which fixed on the table; and finally an inextensible string which connected the car and a small 100g weight that was hanging off the pulley to each other.
Considering the aim is to investigate the relationship between Force, Mass and Acceleration, we first made sure that there are no other forces acting on the car during the experiment (of course we ignored the air resistance because it is just too small). To compensate for friction, Akash put several ruler under the legs of one end of the table in order to allow the car to move at a constant velocity when given a light push. Then Morley came up with his genius idea of keeping force the same, which is the weight on the other side of the string. Also, we released the car from the same distance to the end throughout the experiment because we tried to keep the displacement constant which would keep the experiment fair. Therefore the only variable we controlled is the mass being added on the car. We started from 0g added mass (the only mass was therefore the intrinsic mass of the toy car), and added 250g increments each time until we reached 2000g. Having so many data points let us keep the effect of errors lowest.
And finally we can prove the formula by judging the change of acceleration, which could be calculated by time, displacement and initial velocity.

As the video shows, this is our set-up of the experiment.

A quite important point was made as we starting the experiment, Morley thought that he should stop the timer as soon as the weight reach the floor instead of the car hit the pulley, because there isn't any pulling force acting on the car after the weight hits the floor, and that part of time is just useless to this investigation.

Eventually, as the "21st century second cleverest man" predicted, the velocity clearly decreased as more weight is added on to car, which is perfectly shown in the video. Considering there are no other factors affecting the whole system, the left side of the formula - F, was constant, and one will increase as the other one decreases in the rest of two factors - A and M, or the opposite way. So I believe these calculations are good enough to prove that the law is perfectly right.

Results: http://db.tt/DdVhLQ0

Written by the "21st century cleverest man" Jack Ge

Humbly edited by Akash Jain
Pulleys with scale, pulleys, how pulleys work, physics

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