Energy on a Rollercoaster /

Name: ______Due Date: ______

Lab Partners: ______

Introduction

Objective

There are two objectives for this lab: 1) document the dynamic interchange of the potential and kinetic energy as the track changes and 2) evaluate the loss in mechanical energy over the length of the track.

Hypothesis

Since there are two objectives there must be two hypotheses.

For the first objective: The potential energy of the ball will be directly proportional to the height of the track and the kinetic energy will be inversely proportional to the height of the track.

For the second objective: Since the track is a real system and the ball is subject to rolling friction, the total mechanical energy of the system will get smaller over time. This will be possible to see when looking at the total mechanical energy of the ball over the length of the track.

Methods

Materials

Metal ball, rollercoaster track, CPO stand, mass balance, meter stick, CPO photo gate, paper weigh boat

Procedure
  1. Set-up the CPO stand and track so that the bottom of the track is level. This required using the fifth hole up from the bottom of the standard CPO stand to support the rollercoaster track.
  2. Measure the mass and diameter of the metal ball using a meter stick and mass balance.
  3. Add a single photo gate to the first location to be measured and use the meter stick to measure the height of the track at the location of the photo gate's electronic eye.
  4. Roll the metal ball down the track taking care to start from rest and at the starting peg on the track. These are important controlled variables for the experiment, and must be consistent.
  5. Record the interval time from the photo gate, and repeat this process at least twice to ensure that the photo gate interval time is correct.
  6. Move the photo gate to the next selected location along the track and record the order of the selected point and begin the measurement process again for that location at step three in these procedures. Repeat this process for all seven selected locations. (Shown to the right)
  7. After completion of the data collection, clean up all materials and return them to their original locations in the lab.

Results

Data

The diameter of the metal ball as measured with a meter stick was ______m. The mass of the metal ball as measured from a mass balance was ______kg. The heights and photo gate time intervals are shown in the table below and have not been altered in any way.

Location description / # / Height above table (m) / Photo gate interval time (s)
Top of track at the top of first hill / 1
Halfway down first hill / 2
Bottom of first valley / 3
Halfway up second hill / 4
Top of second hill / 5
Halfway down second hill / 6
Very last point before end of track / 7
Calculations

There are several calculated values that came from the recorded data. The speed at each photo gate location was calculated by dividing the diameter of the ball by the interval time of the photo gate.

The potential energy was calculated with the equation Ug=mgh and the mass of the ball was used, along with the height of the track above the table and the value 9.8m/s2 for the acceleration due to gravity.

The kinetic energy was calculated by using the equation Ek=1/2mv2 and the mass of the ball and previously calculated velocities at each point were used.

Finally, the total mechanical energy was calculated as the sum of the potential and kinetic energy at each point along the track. These values are all shown in the table on the next page.

Location description / # / Height above table (m) / Photo gate interval time (s) / Speed at location (m/s) / Kinetic Energy (J) / Potential Energy (J) / Mechanical Energy
(J)
Top of track at the top of first hill / 1
Halfway down first hill / 2
Bottom of first valley / 3
Halfway up second hill / 4
Top of second hill / 5
Halfway down second hill / 6
Very last point before end of track / 7

Discussion

Answer these few questions at the conclusion of the lab. There will be a more in-depth look at these results later on through careful graphing and further review and comparison. Hold on to this data.

  1. At what two points did the ball have the most potential energy? At what two points did the ball have the most kinetic energy?
  1. Why is there still some potential energy left when the ball is at the very last (and lowest) point on the track? Can this be corrected, or does it need to be corrected?
  1. Compare the total mechanical energy in position #1 to the total mechanical energy in position #7. Are these values what you expected to find? (Hint: Conservation of Energy)If not, try to explain why they might not be what you expected to find.

Make two preliminary graphs of the kinetic energy and the potential energy over the seven locations.

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