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# Elastic and Inelastic Collisions

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## Jessie Clingerman

on 8 February 2013

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#### Transcript of Elastic and Inelastic Collisions

p = (m + m )(v ) Elastic and Inelastic Collisions Jordan Browning, Margaret McGuirk, Allison Sanphilipo, J.C. Clayton, Kevin Yin, Fred Zhang, Jessica Clingerman Introduction Inelastic Collision Elastic Collision Data Tables (by mass) Sample Inelastic Momentum
Calculations Method Is momentum conserved in elastic and inelastic collisions even if the mass and velocity are changed? Method 1. Measure mass of cart with wooden block and picket fence, record. Repeat for second cart.
2. Set up photogates along track, measure space between gates. Connect to timer, set to "Collision" mode.
3. Start timer.
4. Push carts gently toward each other on track, starting outside the gates and waiting until both carts have passed back through the photogates.
5. Record initial and final velocities for each cart.
6. Repeat steps 3-5 five times.
7. Secure weights to each cart, calculate and record new masses.
8. Repeat steps 3-5 five times with added weights.
9. Secure additional weights to one or both carts, record new masses.
10. Repeat steps 3-5 five times with added weights. 1. Measure mass of cart with wooden block and picket fence, record. Repeat for second cart.
2. Set up photogates along track, measure space between gates. Connect to timer, set to "Collision" mode.
3. Start timer.
4. Push carts gently toward each other on track with Velcro sides facing the center. Make sure carts stick together and wait until they return through one gate. Trigger second gate.
5. Record initial velocities and final velocity of the gate that the carts passed back under.
6. Repeat steps 3-5 five times.
7. Secure weights to each cart, calculate and record new masses.
8. Repeat steps 3-5 five times with added weights.
9. Secure additional weights to one or both carts, record new masses.
10. Repeat steps 3-5 five times with added weights. Materials We believe that momentum will be conserved because of the law of conservation of momentum. However, human error may cause the final momentum to be slightly different. Question: Hypothesis: 1. 2. 3. 4. 1. car 1
2. car 2
3. frictionless track 5. 6. 7. 4. Smart timer
5. 2 photo gates
6. wood blocks & picket fence
7. weights Conclusion Our hypothesis was incorrect. Our initial and final momentum for the elastic and inelastic momentum should have added up to be equal. However, the final momentum was significantly smaller, which indicates a loss of momentum that is contrary to the Law of Conservation of Momentum. This also holds true for the kinetic energy of the elastic collisions.
Both human and mechanical error in this lab could have caused the differences between initial and final momentum. For instance, the "frictionless track" may have had some friction. The wheels of the carts may have been sticky or rough, causing other forces that caused resistance. The collisions of the carts also may have caused the wheels to slide slightly off the tracks, which would also have caused increased resistance as they returned under the photogates. Kinetic energy could have been lost in the sound of the elastic collisions, and any heat or friction caused by the collision.
This lab could be applied to car crashes, which are examples of inelastic collisions. An example of an elastic collision would be billiard balls while playing pool. Materials 1. car 1
2. car 2
3. frictionless track 4. Smart timer
5. 2 photo gates
6. picket fence & wood blocks
7. velcro end
8. weights 1. 2. 3. 4. 5. 6. 7. 8. Sample Elastic Calculations p=mv Pre-Lab Questions What is assumed when stating that the total momentum of the system of colliding objects does not change before and after the collision? It is assumed that there is no friction, so that the law of Conservation of Momentum is applied. How is the conservation of momentum expressed in terms of an equation for a two object collision? What is the expression for kinetic energy in terms of an object’s mass and speed? How is the conservation of kinetic energy expressed for a two object elastic collision? How does an elastic collision compare with an inelastic one? In inelastic collisions, the two objects collide and become one object, for instance when a soccer ball enters a goal. In elastic collisions, the two objects collide and bounce off of one another, remaining two separate objects. p = momentum m= mass v = velocity .623kg * 34.4 m/s = p
21431.2 kg*m/s = p p = mv KE=1/2m(v^2) KE = kinetic energy m = mass v = velocity Momentum and Veloctiy Data
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