Lab 2_2 Energy Losses 2

Agenda Experiment to calculate Static friction coefficient Work on the post-lab data analysis for circular arc and half-horizontal loop while waiting for your team’s turn

Lab Activities (Part 2) Lab Apparatus Ramp (Static 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.

Ramp Apparatus - Slippage In the lab you will determine the value of angle, β, at which the conjoined balls begin to slide down the ramp. W = mg motion β W = mg β NO MOTION Body doesn’t slide Body just begins to slide From β you can calculate ΘC, the angle above which you can expect slippage of a single ball on your roller coaster (with increased energy losses). The calculation is in the lab procedures. Critical angle doesn’t depend on the mass of the object – only on the static friction coefficient This is the third task in the procedure sheet. The students would place the ball pair on the ramp and slowly raise the angle of the ramp to the point when the pair JUST starts slipping. Make sure that the person raising the ramp does not shake or bump it causing the co-joined balls to slide early. Why are we using a ball pair here? The friction is only dependent on the two surfaces (ramp and ball surface) in contact and the angle of elevation. It is NOT dependent on the contact area. By joining two balls, we are preventing the body from rolling. Also ,we are using the same two surfaces for which we are trying to calculate the frictional coefficients.

Vertical Loop Apparatus – G force NOTE: We will not actually have the students use this device Design Considerations for a Vertical Loop: Why do you need to calculate separately from the bottom to the top of the loop and from the top to the bottom of the loop? Ans: You need to check at the top of the loop to see if V < (gR)½, in which case the ball will lose contact with the track. If the velocity is only a little bit low, it may not be obvious when watching the ball, but will throw off energy loss calculations. For consideration only, you will not be actually using this device in the lab.

Assignments and Reminders The post-lab data analysis should be emailed to instructor by midnight on Friday. Use Cell Referencing! Instructor will send your team comments based on your calculations. Therefore you will have the correct results for the memo. Weekly lab checklists, Memo Grading Guidelines and Lab Participation Agreement must be included with the weekly memos. Lab Memo 2 (team) is due in Lab 3 Update Project Notebook