1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Mechanical energy of a wooden block sliding down an incline.

  1. Nov 18, 2013 #1

    Kot

    User Avatar

    1. The problem statement, all variables and given/known data
    A wooden block is on an incline with θ = 18.5 degrees. The angle was determined to be big enough that the wooden block would experience kinetic friction ( slides down the ramp). A photo-gate was used to measure the time it took for the block to move a certain distance. Five different trials are performed each time moving the block an increment of 10 centimeters away from the photo-gate. The distance of the block from the photo-gate are 0.2m, 0.3m, 0.4m, 0.5m, and 0.6m. The time it takes the block to pass the photo-gate is 0.31s, 0.31s, 0.313s, 0.36s, and 0.32s respectively. The velocities of each trial are about 0.18m/s for each trial. These values were calculated when I did my lab. I am supposed to calculate the kinetic energy, potential energy due to gravity, total change in mechanical energy and graph them in terms of the displacement.


    2. Relevant equations
    K=1/2mv2
    U=mgh

    3. The attempt at a solution
    I was able to calculate the kinetic energy, potential energy and total change in mechanical energy of the wooden block. When I graphed displacement over change in total mechanical energy the graph was a line and had a negative slope. I assume that it is negative because the wooden block is losing energy due to friction while it travels down the incline so this results in a graph with a negative slope, is this correct?
     
  2. jcsd
  3. Nov 18, 2013 #2

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Yes, but I'm surprised you always saw much the same speed. In fact, it seems to get slower as the run-up increases. Why is one time to 3 places of decimals and the others only to 2?
    Seems to me your timings aren't precise enough to conclude much.
     
  4. Nov 18, 2013 #3

    Kot

    User Avatar

    I rounded the times down and accidentally left that part in. Looking back on the graph I do find the velocities decreasing slowly. I think this was due to the equipment because on some trials we would get a significantly faster velocity than the previous trials at the same distance.
     
  5. Nov 19, 2013 #4

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Something might have been changing... getting warmer, or damper etc. Maybe you should have repeated the set of distances a few times to see if there were any trend against passing time.
     
  6. Nov 19, 2013 #5

    Kot

    User Avatar

    I will keep that in mind next time. I am unable to perform this experiment again at this time. I guess I have to state the error in my lab report.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Mechanical energy of a wooden block sliding down an incline.
Loading...