Kevin Nguyen
Lab Partners: Kevin Tran, Jose Rodriguez
Date lab was performed: April 12, 2017
Purpose of the lab: The purpose of this lab is to observe and verify the impulse - momentum theory (J = delta p) in two different collisions: elastic and inelastic.
Theory:
Experiment 1:
For this experiment, we attempt to verify the impulse-momentum theory in an elastic collision. We measured impulse by using the data the force sensor collects over that short period of time. We measured the initial and final momentum by measuring the mass of the cart with the force sensor and the velocity before and after the collision. Since impulse equals final momentum minus initial momentum, we verified the impulse momentum theory by using the equation "Force * Time = Final momentum - initial momentum."
Experiment 2:
We repeated experiment one except we added additional mass onto the cart.
Experiment 3:
In this experiment, we verified the impulse-momentum theory of an inelastic collision. We did so by recording the force acted on the cart over time to find impulse. We recorded the mass and just the initial velocity of the cart in order to get its momentum. We didn't need to record the final velocity since the cart stays stuck there after colliding with the clay. We compared the value for impulse and momentum and see if they are the same (or similar) to verify the impulse-momentum theory.
Summary:
To set up the first experiment, we set it up like the picture below.
At the top of the picture, although it is not clear, the student is calibrating the force sensor so it can take accurate measurements. The track is laid and positioned so that it is parallel and under the cart with the springy bit towards the other end of the track.
The springy bit was positioned so that it hit the rubber extension of the force sensor in order to create an elastic collision. We put a motion detector at the opposite end of the track so that it can record the initial and final velocity of the cart. We set the positive direction towards the motion sensor so that the initial velocity is recorded as negative. We did this so that subtracting the initial and final momentums doesn't give us a negative value. We made the track leveled to prevent the velocity from being affected by outside sources other than our gentle push. After recording our data, we made a force vs time graph (to measure impulse) and a velocity graph (to measure initial and final velocities). These graphs are shown below.
For experiment 2, we added 500g to the cart with the force sensor and repeated the procedure.
For experiment 3, we set up the lab like the pictures below.
For experiment 3, we kept the 500g mass on the cart. We set the wooden block with clay at one end of the track and a motion sensor on the opposite end of the track (not shown in the third picture). We attached a nail to the force sensor (with the pointy end sticking out) so that the cart can "stick" to the clay to create an inelastic collision. We then gave the cart a gentle push and recorded the data after the collision is finished. We made a Force vs time graph and a velocity graph. They are shown below.
Measured/ calculated data:
Experiment 1:
Experiment 2:
Experiment 3:
Explanation of graphs:
Since we used force vs time and velocity graphs for all three experiments, I will explain what they all do as a whole. The reason why we used a force vs time graph was because integrating the force vs time line from the point the force starts to increase to the point where the force returns to zero gave impulse. We used the velocity graph to find initial and final velocities of the cart by placing the velocity graph directly above the force vs time graph. We then recorded the initial velocity and final velocities by aligning the point the force begins to increase with the initial velocity and the point the force returns to zero with the final velocity.
Conclusion:
Overall, all three experiments were very successful. The values for impulse was very similar to the values of delta momentum. Although the values of impulse were very similar to the values of delta momentum, they were not exactly the same. This uncertainty may stem form multiple factors. One of the factors is friction of the track since the friction of the track decreases the cart's velocity, which will lower the initial and final velocity and therefore slightly affecting the value for momentum. Air resistance may also affect the cart's velocity since air resistance slows down the cart.
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