Pulley experiment

  Have  you ever being in a class where  a formula  is given  to you and you  just have to trust that  whatever was given to you is always true? Fortunately, this wasn’t the situation for For this weeks experiment using the  Lego Mindstorm motor; we actually tested Newton’s second law (F=ma); the law of conservation of energy (E=mgh);  and their relationship with velocity, acceleration and power. Our system consisted of a pulley system with weights attached to one end  the motor  on the other end.  Using the Mindstorm software we were able to control the power of the motor  among other values that  were part of our system such as mass and  rpm.

  Our first consisted of on setting the power level of the motor to a  constant value of 75 Watts and changed  and increased the mass values . We wanted to observe id the acceleration value changed  with the increase in mass. These  are  our results :

Another way to see these date if through a graphical representation , which you can see below. You will notice  that  there is a  big difference between  the slopes from   the first 2   masses and  the third one; the reason for is is exactly that: instead of making a small increment on the masses values, we made a big change and went from 160 grams t0 200 grams

 Then we continued to our next experiment ,which involved  the same procedure  as before but this time  we kept the mass value  constant ( 100 grams ) .We increased the power level and  recorded the acceleration values. The table  below shows the final  results :

And here is our graphical representation of these results:

  From the results from above you can clearly see how and increment in the power will result in an increment of the acceleration if the mass value is kept constant.

  For the second part of our lab we  explores the law of conservation of energy by using the following formula: Potential Energy =mgh. Keeping a constant power level like before  (75 W) and a reference height of 0.2 m (20 cm) we were able to calculate the potential energy  for each scenario ( different masses).Once our potential values were calculated we  were able to calculate the power user by the motor through the following formula :

The table below shows our final results  for potential energy and power used:

As you can see  from the table above  and increase in mass will results in  higher values for the potential energy and the power used; which results in a higher level of  battery discharge meaning that our stored energy will get   used faster when lifter higher  quantities of mass than  when lifting smaller masses.

I think it is safe to conclude that after all of our  results from our experiment, that those formulas that we received at the beginning of our lecture ; Newton’s second law  and conservation of energy ; are true.What do you think ?