1. Lab Safety Policies Don’t stand on lab chairs
Don’t sit or stand on lab tables
No dangling jewelry or loose clothes.
No open toed shoes.
Be careful with sharp corners.
Recall location of phone and first-aid kit.
Report ALL injuries
Point out where the phone and first-aid kit are located – make sure the first aid kit is turned so it is easily visible.
Report all injuries that occur in your lab to one of the lab supervisors.

2. Lab 2_1 Energy Losses 1

3. Recap of previous lab Law of Conservation of Energy
Energy can neither be created nor destroyed
Energy can transfer from one form to another
Examples of Energy Losses are the following:
Resistive forces, such as friction and air resistance
Act on a body in motion and cause energy to be transferred to unwanted forms (i.e. heat).
For the roller coaster ball,
𝑃𝐸 1 + 𝑇𝐾𝐸 1 + 𝑅𝐾𝐸 1 = 𝑃𝐸 2 + 𝑇𝐾𝐸 2 + 𝑅𝐾𝐸 2 +"𝐸𝑛𝑒𝑟𝑔𝑦 𝐿𝑜𝑠𝑠𝑒𝑠"
Briefly review the various key concepts that students learned in Lab 1. Answer any questions that the students have before continuing with this lecture.

4. Recap of physics reading module
Friction is a process that results in a force that opposes an action.
Static Friction (acts to prevent motion)
Kinetic Friction (exists between moving surfaces)
Sliding Friction (due to sliding action of the object)
Rolling Friction (due to rolling action of the object)
Friction causes your ball to lose energy as it traverses along the track.

5. Recap of physics reading module
Slippage results from a steep angle causing the ball to slide rather than roll.
Sliding friction is generally greater than rolling friction.
Curved Motion
Critical velocities:
At the top of a loop:
At the top of a bump:
Bank angle creates the centripetal force needed to keep the ball on the track.

6. Agenda Day 1: Experiments to calculate rolling friction coefficient
Experiments to calculate average G-force
Day 2:
Experiments to calculate static friction coefficient
Working on post-lab data analysis

7. Roller Coaster Energy Analysis Spreadsheet
You will be using a RC Energy Analysis Spreadsheet to model most, but not all of the energy losses that your coaster will experience.
This Excel spreadsheet allows for
Vertical loops/curves
Bumps
Horizontal loops/curves
Relatively straight sections of track
Energy losses due to friction, G-forces and air resistance are included.
The roller coaster track needs to be broken into appropriate sections and analyzed piece by piece. This will be discussed more in the basics presentation dealing with the Roller Coaster Analysis Spreadsheet

8. Additional Energy Losses
Snap-fit spacing - Too wide a spacing can cause excessive energy losses through track deformation.
Structural stability (including track) - An unstable structure can cause energy losses through movements within the structure. Bending of the track can also cause energy losses.
Differential forces between rails along horizontal curves –The ball will exert a different amount of force on each rail of the track.
Other losses, mainly deformation of the track due to inadequate track support and deformation of the support structure are too design dependent to be included in a design spreadsheet. Students need to design to minimize these losses given the limits on the number of parts. They need to think about how these additional energy losses will affect their designs.

9. Lab Activities (Part 1) Lab Apparatus Circular Arc (Rolling Friction)
Group Rotation
Data will be collected at the front table by each team.
Each team will take turns rotating to the table and collect data with one ball on a total of three apparatus.
Each group will be notified when it is their turn to rotate to the front table.
Each group should record their data on the printed worksheet at the front table and on the computer at the instructor’s station.

10. Circular Arc Apparatus - Friction
Ball is released at point A.
The type of motion (oscillation, simple harmonic motion) is a way to roll a ball a relatively large distance with a relatively small apparatus.
Ball oscillates for some time and eventually comes to rest –Why? A
Show the students a demo and invoke a discussion.
This is one of the Circular Arc apparatus that the students will be using in lab. We are trying to explain a few concepts with the help of this experiment.
The rolling friction loss per meter of rolling is a relatively small quantity. To better quantify it, a longer travel distance is required. We use simple harmonic motion to provide a small apparatus with ‘large’ travel distance.

11. Lab Activities (Part 2)
This activity will be done at your table during the entire lab period.
Locate your sample build kit, speed sensors, Arduino board.
Build the support structure and track.
Take measurements for four cases.
Analyze, graph, and discuss your results.
Circuits Lab 2

12. You'll make this support structure

13. Experimental Setup
You'll add speed sensors at the beginning and end of the horizontal curve and measure the energy losses for different starting points.
Sensor B
Sensor A

14. Speed Measurement Accuracy
Tests of production speed sensors show an accuracy of about +/- 2% when using a correction factor of This is with the LED and photo-transistor visually aligned.
Visually confirm that the glued alignment of the two LEDs is correct.
If not aligned, errors of up to 10% can occur!

15. Let’s put things together!
Energy losses on straight track:
Frictional forces
Air resistance
Additional energy losses:
Snap-fit spacing
Structural stability
Differential forces between rails
A ball following a curved path:
Involves centripetal force.
Has different frictional losses than when rolling on straight track.
Special cases of curved sections of track are vertical and horizontal loops.

16. Assignments and Reminders
The post-lab data analysis spreadsheet will be due at midnight next Friday for instructor to check your calculations.
You will have some time to work on the data analysis in the lab session next week.
If you can finish the calculation for circular arc and half-horizontal loop before the lab, the instructor can help your team check the results during the lab session.