Lab 8 Physics

Siena College - General Physics 110 Collisions Lab NAME: David Rivera GROUP MEMBERS: Derek, Steven Learning Goals 1. In Section I, you will investigate if any physical quantity (or quantities) remain the same both before and after a collision for a two-cart system. 2. In Section II, you will test the physical quantity that you’ve determined remains constant in Section I’s experiments to make a prediction of the ratio of Eugenia’s and Bor’s speeds (v Eugenia / v Bor ) after Eugenia pushes Bor 3. In Section III, you will use your knowledge of impulse to explain the motion of the carts in the video and estimate the impulse and force that the air exerts on the carts. 4. In Section IV, you will estimate the change in the total mechanical energy of a 2-cart system and explain what other forms of energy it was converted into. In addition, you will also explain the mechanism that made one of the carts speed up after it momentarily came to rest. Section I - In this part of the lab, you will investigate if any physical quantity (or quantities) remain the same both before and after a collision for a two-cart system. Equipment: Graphical Analysis, dynamics track, 2 Vernier Go Direct carts, magnetic bumpers, velcro bumpers. Scientific Ability Missing Inadequate Needs Improvement Adequate G4 Is able to record and represent data in a meaningful way The data is either absent or incomprehensible. Some important data is absent or incomprehensible. The data is not organized in tables or the tables are not properly labeled. All important data is present, but it is recorded in a way that requires some effort to comprehend. The tables are labeled, but the labels are confusing. All important data is present, organized, and recorded clearly. The tables are labeled and placed in a logical order. B7 Is able to identify a pattern in the data No attempt is made to search for a pattern. The pattern described is irrelevant or inconsistent with the data. The pattern has minor errors or omissions. The pattern represents the relevant trend in the data. 1

Siena College - General Physics 110 Collisions Lab Set-up and run the following experiment with a two-cart system. A. Cart A, loaded with a 1 kg block, moves to the right at a gentle constant speed and hits a stationary and empty Cart B. Ensure that magnetic bumpers are attached to each of the carts. [ https://youtu.be/HbMBplGL3Zo ] Use the table that follows to help you investigate if any physical quantity (or quantities) remain the same both before and after a collision for a two-cart system. Physical quantities ⟶ Mass m Speed v x- velocity component v x Mass times speed mv Mass times x- velocity component mv x ½ times mass times speed squared (½)mv 2 Line 1: Cart A ( before collision) 1309 g 0.248 m/s .242 316.77 8 316.778 38.33 Line 2: Cart B ( before collision) 299g 0 m/s 0 0 0 Combined physical quantity for Cart A & Cart B (add line 1 and line 2 for each quantity) 1608 g .487 m/s .242 316.77 8 316.778 38.33 Line 3: Cart A ( after collision) 1309 g 0.129 m/s 0.129 m/s 168.86 168.86 10.89 Line 4: Cart B ( after collision) 299g 0.366 m/s 0.366 m/s 109.43 109.43 20.03 Combined physical quantity for Cart A & Cart B (add line 1608 g 0.366 m/s 0.237 m/s 278.29 278.29 30.92 2

Siena College - General Physics 110 Collisions Lab Line 4: Cart B ( after collision) 299 g 0.003m /s - .003 0.897 -0.897 0.00135 Combined physical quantity for Cart A & Cart B (add line 3 and line 4 for each quantity) 599 g 0.006 m/s 0 1.797 0.003 .0027 Circle or highlight the combined physical quantity or quantities that remained the same both before and after the collision for the two-cart system. Set-up and run the following experiment with a two-cart system. C. Cart A, loaded with a 1 kg block, moves to the right at a gentle constant speed. An empty Cart B moves to the left at the same gentle constant speed as Cart A. The carts collide and stick together. Ensure that velcro is attached to each of the carts. [ https://youtu.be/tciBA4w4ZiU ] Use the table that follows to help you investigate if any physical quantity (or quantities) remain the same both before and after a collision for a two-cart system. Physical quantities ⟶ Mass m Speed v x- velocity component v x Mass times speed mv Mass times x- velocity component mv x ½ times mass times speed squared (½)mv 2 Line 1: Cart A ( before collision) 1309g 0.316 m/s 0.316 m/s 413.64 413.64 65.36 Line 2: Cart B ( before collision) 299g 0.271 m/s -0.271 m/s 81.03 -81.03 10.98 Combined physical quantity 1608g .587 m/s .045 m/s 494.67 332.61 76.34 4

Siena College - General Physics 110 Collisions Lab for Cart A & Cart B (add line 1 and line 2 for each quantity) Line 3: Cart A ( after collision) 1309g 0.152 m/s 0.152 m/s 198.97 198.97 15.12 Line 4: Cart B ( after collision) 299g 0.151 m/s 0.151 m/s 45.15 45.15 3.41 Combined physical quantity for Cart A & Cart B (add line 3 and line 4 for each quantity) 1608g 0.303 m/s 0.303 m/s 244.12 244.12 18.53 Circle or highlight the combined physical quantity or quantities that remained the same both before and after the collision for the two-cart system. After you come up with a physical quantity that is the same before and after each collision, decide which quantities remain constant in ALL FOUR experiments. Section II - In this part of the lab, you will test the physical quantity that you’ve determined remains constant in Section I’s experiments to make a prediction of the ratio of Eugenia’s and Bor’s speeds (v Eugenia / v Bor ) after Eugenia pushes Bor. Equipment: Video in part (c). Scientific Ability Missing Inadequate Needs Improvement Adequate A9 Mathematical No representation is constructed. The mathematical representation lacks the algebraic part (the student plugged in the numbers right away), has the wrong concepts being applied, signs are incorrect, or progression is unclear. No error is found in the reasoning. However, there may not be fully completed steps to solve the problem or one needs considerable effort to comprehend the progression. No evaluation of the math in the problem is present. The mathematical representation contains no errors and it is easy to see the progression from the first step to the last step in solving the equation. The solver evaluated the mathematical representation. C8 Is able to make a No judgment is A judgment is made, A judgment is made, A judgment is made, 5

Siena College - General Physics 110 Collisions Lab 3:2 D. Make a judgment about whether the experimental measurement agrees with your prediction for the ratio of the two speeds. What can you say about your confidence in the new physical quantity that you used to make the prediction? The experimental measurement does agree with our prediction for the ratio of the two speeds, we see the ratio of 3:2 present in our date table, which is very close with our prediction, which was 1.296. Every second Eugenia goes about 90cm, and Bor goes about 60 cm. We are confident in our new physical quantity due to the fact that it’s slightly off from our predicted quantity. Section III - In this part of the lab, you will use your knowledge of impulse to explain the motion of the carts in the video and estimate the impulse and force that the air exerts on the carts. Equipment: Videos in parts (a) and (b). Scientific Ability Missing Inadequate Needs Improvement Adequate A11 Graph No graph is present. A graph is present, but the axes are not labeled. There is no scale on the axes. The data points are incorrectly connected to each other instead of using an appropriate trendline. The graph is present and the axes are labeled, but the axes do not correspond to the independent and dependent variable OR the scale is not accurate. The data points are not connected to each other, but there is no trendline either. The graph has correctly labeled axes, the independent variable is along the horizontal axis and the scale is accurate. The trendline is correct. A9 Mathematical No representation is constructed. The mathematical representation lacks the algebraic part (the student plugged in the numbers right away), has the wrong concepts being applied, signs are incorrect, or progression is unclear. No error is found in the reasoning. However, there may not be fully completed steps to solve the problem or one needs considerable effort to comprehend the progression. No evaluation of the math in the problem is present. The mathematical representation contains no errors and it is easy to see the progression from the first step to the last step in solving the equation. The solver evaluated the mathematical representation. A. Use your knowledge of impulse (Net Impulse = F Environment on System Δt = mv f - mv 0 ) to explain the motion of the carts in the video below (specifically, identify the object that exerts the impulse on the carts) and to predict the shape of the velocity-vs-time graphs in the following experiments: [ https://youtu.be/LEHPPXRwLX4 ]. We predict that the longer the time that the fan runs, the faster the cart will 7

Siena College - General Physics 110 Collisions Lab go. Resulting in the graph showing a positive correlation between velocity and time. The object that’s exerting the impulse on the cart is the fan, which the air flows behind the cart making it move forward. B. Watch the following video [ https://youtu.be/AB2F3yukAkE ] to compare your prediction to the outcome. Discuss the differences if any occurred. Our prediction matched the outcome because the graph shows that as the fan ran for a longer time, the velocity of the carts increased. C. Use the graphs and other data from the video above to estimate the impulse and force that the air exerts on the carts. Check if this force is the same in all experiments. Should this force be the same or different? How do you know? The force that is exerted on the cart increases 40 newtons per second. After 2 seconds for would be at 80N/s, at 3 seconds it would be at 120N/s, and so on. Net Impulse = F Environment on System Δt = mv f - mv 0 ( 400(.1))-400(0) = 40N/s Section IV - In this part of the lab, you will estimate the change in the total mechanical energy of a 2-cart system and explain what other forms of energy it was converted into. In addition, you will also explain the mechanism that made one of the carts speed up after it momentarily came to rest. Equipment: Video. Scientific Ability Missing Inadequate Needs Improvement Adequate B9 Is able to devise an explanation for an observed pattern No attempt is made to explain the observed pattern. An explanation is vague, not testable, or contradicts the pattern. An explanation contradicts previous knowledge or the reasoning is flawed. A reasonable explanation is made. It is testable and it explains the observed pattern. You have two low-friction carts on a track. You fix a metal rod on cart B and a plastic box on cart A. Cart A has a spring bumper that compresses and expands elastically. You put some sugar mixed with a few steel ball bearings in the box on cart A (see figure below). 8

Siena College - General Physics 110 Collisions Lab The total momentum of the system was not kept constant. What caused the total momentum change was the sugar, ball bearings, and the spring in front of the cart. The reason I say this is because the loss of momentum caused by the spring was not regained but the material above cart A, causing it to move at a constant speed after collision. Mechanical energy was kept constant throughout the system, because before collision the amount of potential energy stored in the carts were the same, and at the time of collision the energy was transferred. B. At t = 0.35 s, cart A almost stopped moving but after that time it sped up and continued moving with constant speed. Explain the mechanism that made cart A speed up again. (Hint: watch the video and carefully observe cart A during the collision.) The sugar and the ball bearings above cart A is what prevented it from moving forward at a faster speed after contact. The sugar and ball bearing were on one side of the the box before collision, then after collision the material hit the other side of the box and once it stopped moving it transferred that energy to the cart, making it move at constant speed after collision. 10