EXPLORING ENERGY LOSS

NOTES:

Regarding your data tables:

  1. Many of us had sample rates of around .02 sec with means 50 data points per second. Please do not throw all of that data into your data table. Most of that is irrelevant so please make sure to include only the relevant. data in your table.
  2. If you throw a massive amount of irrelevant data at me it will cost you.
  3. If you took the mass of the cart be sure to include it in your data table.
  4. Since you will be doing calculations involving that data, show the RESULTS of those calculations on that data table.
  5. Be sure to show relevant averages. You will use the average data as a basis for your Discuss io
  6. Due to our ability to take rather precise data I will be looking for consistent data.

LAB SPECIFIC INSTRUCTIONS:

  1. This is a 'regular' lab in that all points are as expected in the class Lab Rubric and Sample Lab.
  2. We are ONLY concerned with the energy lost during the collision. Energy lost to friction as the cart slides other than during the collision is immaterial.
  3. You should indicate where the energy loss occurred in the REASONING section of your discussion. A brief discussion of the physics of the situation is required.
  4. A graph is neither requested nor required (That means DON'T DO A GRAPH!) since graphs are best at showing trends in changing data. Our goal here is to have clear and consistent data.
  5. Your error analysis should include a conversation about any sort of *inherent* error that you can't avoid. Error discussions about how the equipment might be off or of human error are not as relevant.

 

OPENING QUESTION:

Please work with your team to derive the equation that you will use to determine the loss of energy during a collision between one of our lab carts and the plastic 'backstop' barrier. You will need to make certain assumptions, please make sure you understand those and include those in your lab write-up.

BACKGROUND (From Yesterday):

Consider the case of a a lab cart moving along a smooth (but NOT frictionless) track.

  • The cart can be placed in motion by pushing a button (and something else you'll figure out pretty quickly)
  • The cart has *built in* motion (displacement and velocity) and accelerometer sensors. They are very cool!

We'll be MOSTLY having what I call a 'sandbox' day today since it is a short day. You'll be working with your team to learn how the sensors work and explore the various types of data you can take with those sensors.

We're going to assume that energy lost to air friction is minimal. I did a wee bit of research and it appears that energy lost by a Vernier Lab Cart sliding across a smooth, Vernier aluminum track is on the order of a milliJoule (~.001 J).

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Work for Day #2:

I suggested yesterday that 'launching' your cart at a consistent velocity was less of a concern since we were only concerned with a very narrow window of time:

Please check your data, does that assumption hold?

If it doesn't you'll need to introduce a 'control' variable to assure that your car is launched with as close to the same speed as you can on every trial.

We did some practice yesterday measuring a 'magnetic' collision in which the cart was 'gently' repelled by the magnetic force between opposing N/S magnets.

Today we'll be measuring an actual collision. That means turning the cart around so that the spring 'plunger' directly contacts the plastic backstop and an actual physical collision can be measure precisely.

We can (and SHOULD) measure data very precisely with the equipment we have in this lab. If something unexpected happens (you bump the table or the cart misbehaves going down the track or anything like that) discard the trial and start again.