Impulse Lab - lab PDF

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Kevin Allen Partner: Ron Mastrocola Impulse and Momentum in Collisions 1410L-813 Alvin Kow 4 April 2017 Objective: The purpose of this lab is to examine elastic and inelastic collisions based on change in momentum which affects the forces involved in the impact. These tests can show ways to better survive car crashes.

Introduction: In this experiment, an apparatus will be used to measure the velocity of the car and the force of the impact over time and graph the results. The test was performed with two springs of different spring constants, no spring, and an airbag made from an inflated sandwich bag. The impulse can be calculated by taking the area under the force-time graph and is represented by the integral ∫ F dt = ∫ dp = mvf - mvi In an elastic collision, the two bodies bounce off each other, therefore the resulting change in momentum is shown by ∫ F dt = -2mvi In an inelastic collision, the object is brought to rest by the force of the impact, therefore the resulting change in momentum is shown by ∫ F dt = -mvi Materials: 1. Collision apparatus 2. Springs and airbag 3. Computer

Diagram:

Procedure: The car was impacted with four things in this experiment. A light spring, a heavy spring, an airbag, and no spring. Each time, the force and velocity were measured and graphed against time. The results were put in a table showing final and initial velocity, change in momentum, impulse, the percent difference and the max force for each run. In the light spring test, the test was repeated three times In the heavy spring test, the test was repeated two times

In the airbag test, the test was repeated three times In the no spring test, the test was repeated two times Results and Analysis: Table 1 – Light Spring Mass of Car-641.8g

Run 1 Run 2 Run 3

Vf (m/s) -0.619 -0.617 -0.631

Δp (kg m/s) 0.9877 0.8895 0.9563

FΔt (Ns) 0.9354 0.6641 0.9088

Vi (m/s) 0.776 1.136

Vf (m/s) -0.575 -0.769

Δp (kg m/s) 0.8671 1.2226

FΔt (Ns) 0.8264 1.1487

Vi (m/s) 1.032 0.992 0.947

Vf (m/s) -0.145 -0.039 -0.067

Δp (kg m/s) 0.7554 0.6617 0.6508

FΔt (Ns) 0.5341 0.6097 0.5762

Vf (m/s) -0.480 -0.324

Δp (kg m/s) 0.8067 0.7612

FΔt (Ns) 1.572 0.5737

Vi (m/s) 0.920 0.769 0.859

% diff 5.3% 4.97% 25.34%

Max Force (N) 37 11 41

Table 2 – Heavy Spring Mass of Car-641.8g

Run 1 Run 2

% diff 4.69% 6.04%

Max Force (N) 21 31

Table 3 – Airbag Mass of Car-641.8g

Run 1 Run 2 Run 3

% diff 29.29% 7.86% 11.46%

Max Force (N) 7.1 9.5 11

Table 4 – No Spring Mass of Car-641.8g

Run 1 Run 2

Vi (m/s) 0.777 0.862

% diff 43.44% 24.63%

Max Force (N) 55 28

Analysis: As shown by each of the graphs of force vs. time, the area under the graph is equal to the impulse of the collision. This value should be very close to the calculated change in momentum since by definition, they are equal.

Discussion: The results obtained from the experiments follow closely with what was expected through calculations. The percent difference of the calculated change in momentum and the impulse derived from the graph is relatively low. The error in the measurement could possibly be from experimental uncertainty since the car loses some of its momentum due to friction. Another thing that could have gone wrong would be that the end button was hit too soon which can cause the measurements to be off.. In order to improve the accuracy of the results for future trials of this experiment, more care can be taken when choosing when to hit the end button, and the apparatus could be improved by reducing friction on the car with wheel bearings and the initial velocity can be kept more consistent. Conclusion: The results from the lab successfully helped to learn more about the difference between elastic and inelastic collisions, and how each of them compare in regards to change in momentum and max force. Questions: 1. In a car crash, the safety features such as the crumple zone, the seat belt, and the air bag help improve the driver and passengers chance of survival. They are all designed to take most of the energy from the crash away from the driver and passenger. The airbag and seat belt help to take the force away from the driver and int the car. The crumple zone helps to take the force from the car and into whatever its hitting. 2. P = mv t = 2d/(V1+Vf ) 34km/hr = 9.44 m/s p=566.4 a. Dashboard: t = 0.00424 F = 133584.9N b. Airbag: t = 0.0847 F = 6687.1N A lot smaller force...