Lab 8 (Impulse and Momentum) PDF

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Eighth lab report in Sup's course...

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Individual Report: Impulse and Momentum Analysis of Results: The results were expected in that our calculated impulse was close in value to our change in momentum and it was predicted that they should be equal based on our theoretical calculation. The error was not very large; the percent difference between calculated impulse and change in momentum was 3.20% and 4.96% for elastic 1 trial 1 and 2 respectively and 0.93% and 0.72% for elastic 2 trial 1 and 2 respectively. The experiment was valid since we accomplished our objective to measure a cart’s momentum change and compare to the impulse it receives and compare average and peak forces in impulses. We found impulse and compared it to our change in momentum for the cart. The major trend in the data was that our impulse calculated by average tension force applied to the cart multiplied by the duration of the impulse was lower in both trials for both elasticities compared to the change in momentum calculated by the final velocity minus the initial velocity multiplied by the mass of the cart. The practical implications of these results are that it has become easier to understand/see how the impulse of an object compares to the change in momentum, which should be equal, but have error in real life. Actually observing this phenomenon of impulse and seeing what it really is in real life and not just in equations or simulations helps me to understand the way it exists with respect to objects in the world around me. Improvement: The major sources of error in this experiment came from the uncertainty/random error that the technology and tools used to calculate the values in this experiment since there was almost no direct human manipulation that could have influenced the values with respect to oneanother. With this in mind, it would be very hard to improve upon this error and do anything to decrease the error with what we have available in lab. Performing more trials would help reduce random error in the experiment, though, and would have allowed us to find an average that was more accurate. However, we only calibrated the force sensor and not the motion sensor so calibrating that sensor could have given us a more accurate velocity reading that would have been used to get a closer value to the calculated impulse and reduce our error. The error in this experiment can be explained by random error in part in all variables influencing the impulse (measurements of force, time, mass, and velocity), though specifically the calibration of the motion sensor could have reduced our error because if a more accurate velocity measurement would have read the values of initial velocity and final velocity as closer, resulting in a smaller value of mass times the difference, decreasing the value of momentum final minus momentum initial and yielding smaller values for this calculation as per the formula used: F x (delta t)= mvfmvi. This would help to decrease the trend noted that these calculated values on the right side of the equation were larger than the left side of the equation for impulse. Individual Questions: To answer the preliminary questions, in question 1 air bags increase the time you are decelerating so you are moving at a slower speed when you collide with the dash because the air bags gives you a larger area/time to do so. This prevents injury because you collide slower than

if you were only decelerated as you are by smashing into the dash. In question 2 the ball would apply a larger impulse to the door because the rubber ball would have a larger change in momentum since rather than going from speed x to 0, the ball goes from speed x to a negative velocity and they both have the same mass so according to mvf-mvi it would have the larger impulse and therefore the ball would be more likely to close the door. For the analysis questions we answered the first three in the group report so for question 4 our peak value of force was 2.88 and average force was 1.966. I would say this is a significant difference as it is a 144% increase from the value of average to peak force. Our same value of impulse could be delivered with a much smaller force by just putting forth a smaller force for longer period of time. The average force could then be much lower but just applied over a much longer period of time shown by our equation F x (delta t)= impulse. For question 5 we were to revisit the preliminary questions and I still believe what I wrote for them originally is correct with regards to what we learned during this lab about the impulse momentum theorem. For question 6 when we used different elastics, the same general shape was observed for both one and two rubber bands. Although, with less elasticity the graph is more stretched length wise and shorter because of less peak force, while when there was more elastic force available to resist the cart moving it was shorter in length but higher in peak force so there was a correlation between the elasticity and the shape. For question 7 the durations of the impulses were affected by the elasticities. The less elastic the material the shorter the duration of the impulse so two rubber bands reduce the duration of the impulse to a shorter time period compared to one rubber band. Although, the maximum size of the force increased with less elasticity so with two rubber bands the peak force was higher than with one rubber band. So in short, more elasticity increases the duration of the impulse, but reduces the peak force....