Effect of Different Masses on the Time it takes for Cart with Sail to Roll Down an Incline


Haley Harrington, Cameron Atkinson, Cameron Springer

Background / Question and Variables / Materials / Picture of Set-Up / Procedure / Data Table / Graph / Conclusion / Bibliography / Other Links / Return to Research

Background (Top)

            When an object rolls down an incline plane, it gains momentum which increases the acceleration. Since Force = (Mass)(Acceleration), if you increase the mass of the object, then the force will increase and the cart will roll down the incline faster (IB Data Packet). Therefore, when you increase the weight (mass) of an object rolling down an incline plane, then the time it takes for the object to roll down this incline plane will decrease.



Question and Variables (Top)

            In this lab, we studied the effect of adding different masses to a cart with a sail on the time it takes for this cart to roll down a 3 meter steady inclined plane. Will the different masses affect the time it takes for the cart with a sail to roll down the inclined plane? Our independent variable is the added mass to the cart and our dependent variable is the time it takes for the cart to roll down the 3 meter inclined plane. Our constants are the length of the incline (3 meters) and the starting mass of the cart with the sail (1178.7 kg.).



Materials (Top)

  1. Cart with sail (1178.7 kg. ± 0.0005)
  2. Variety of 0.5 kg. and 1 kg. masses to use when adding on weight to cart (±0.0005)
  3. Meter stick to measure incline
  4. Inclined plane (steady) (3 meters ± 0.005 m)
  5. Timer
  6. Tape to mark starting and stopping points



Picture of Set-Up (Top)

IB Lab Write Up.jpg


Procedure (Top)

            To set up the lab, we first found a steady inclined plane that was free from any bumps or sticky spots: we used the incline right at the end of the physics hallway by the stairs. Then we obtained our cart with the sail and the collection of 0.5 kg. and 1 kg. weights that we used when adding weight to the cart. We set those to the side with your cart while measuring carefully with a meter stick 3 meters down the inclined plane and marked the starting and stopping points with two pieces of tape. Then we got our timer ready and made sure we had something to write down our data on.

            We positioned one person at the top of the incline with the cart and weights, one person at the bottom to time and stop the cart and then one person on the side recording the data. To get each data point, we positioned the cart at the top of the incline and then said out loud “1, 2, 3, go” and the person at the bottom started the timer on “go” at the same instant as the person at the top released the cart with no force. Once the cart reached the bottom, the person at the bottom stopped the timer and then stopped the cart.

            The first 5 trials were done with no added weight to the cart. Then after 5 trials, we added one 0.5 kg. weight to the back of the cart and then repeated the steps in the paragraph above to get 5 more data points with 0.5kg. this time. Each 5 trials, we added on 0.5 kg. more to the cart so that we had 10 different mass variations each with 5 trials.

            To make sure that our constants (length of incline and initial mass of cart) did not change throughout the experiment, we used the same tape lines and started at the exact same spots for every trial and we used the same cart for each trial and ensured that nothing fell off or was missing before each trial.



Data (Top)

Data: Text/Excel






Conclusion (Top)

It is evident in the data that our original hypothesis was supported, which was that the time of the cart to roll down the slope would decrease as the weight on the cart increased. This statement can be justified by the high negative correlation seen in the data. The first data point with a mass of 0 kg on the cart took an average of 3.38 second to roll down the slope, while the final data point, which had an added weight of 4.5 kg took an average of 2.65 seconds. Some weaknesses that our experiment experienced was the times being very inaccurate as we used an iPhone timer. There is a big space for error because of our method for timing isn't very accurate. Another weakness is that it might not have rolled straight down the incline which could have affected the times. A weakness of the procedure is that it is possible that the decline slope was not measured out precisely, which could have impacted times. There are several improvements that could be made to reduce sources of error in our experiment. One improvement to reduce error on timing would be to video record all trial. By doing this, we could get a more approximate time for each trial because we would be reducing human error. Another improvement could be to make a cart that goes straight down the declining plane. It would be interesting to see how much more accurate the data could get. By making these two improvements we could collect more accurate data. Overall, this experiment did a good job of proving that the more mass a cart has, the faster it will roll down a slope.


Bibliography (Top)

Air Friction, hyperphysics.phy-astr.gsu.edu/hbase/airfri.html.

Allain, Rhett. “A Rolling Object Accelerating Down an Incline.” Wired, Conde Nast, 3 June 2017, www.wired.com/2014/07/a-rolling-object-accelerating-down-an-incline/.

“What Are Inclines?” Khan Academy, Khan Academy, www.khanacademy.org/science/physics/forces-newtons-laws/inclined-planes-friction/a/what-are-inclines.

Energy of a Rolling Object, www.webassign.net/question_assets/unccolphysmechl1/lab_6/manual.html.

Forces - Science - Pupils - 3M UK Streetwise - Bright Thinking on Our Roads, www.3m.co.uk/intl/uk/3Mstreetwise/pupils-air-resistance.htm.



Other Links (Top)

Here is a link to a similar lab: http://web.mit.edu/rsi/2012/minisubmit/lkim13/main.pdf.gz

Video that shows what we did and how the cart rolls down the inclined plane: https://www.youtube.com/watch?v=BXJaddSgQNc

Explanation of air friction: https://en.wikipedia.org/wiki/Drag_(physics)

Explains the science behind the lab: https://www.physicsclassroom.com/class/vectors/Lesson-3/Inclined-Planes

How to calculate uncertainty: https://www2.southeastern.edu/Academics/Faculty/rallain/plab194/error.html