Coefficient of Friction Setting up and executing an experiment.

QPOE2 What do you know about the given question How will you apply what you found Question Application Knowledge probe Explanation Evaluate Prediction Data Analysis Investigation plan Observation How will you analyze your data How will you investigate the question

QUESTION Which of the following objects has the greatest coefficient of rolling friction between itself and the carpet floor?

What have we learned that would help us answer this question What have we learned that would help us answer this question? Cart project: the cart stopped because of rolling friction between the wheels and the surface of contact (carpet and wooden floor). Without a breaking system, the negative acceleration (deceleration)is constant or uniform. Those that did have a breaking system had greater friction (sliding friction)once the breaking system kicked in.

What have we learned that would help us answer this question What have we learned that would help us answer this question? The coefficient of static and sliding friction activity showed us that we can calculate m by dividing the friction force by the normal force (mass x acceleration due to gravity).

Equations of Motion for Uniform Acceleration Equations Variables vf = vi + at vi vf a t d = ½ (vf + vi) t vi vf d t d = vit + ½ at2 vi a d t vf 2 = vi 2 + 2ad vi vf a d

Knowledge Probe What do we know about friction? How do we calculate the coefficient of friction? Which kinematic equations would help us? What materials do we need? What values are we going to measure? What types of errors should will we encounter? How many measurement should we take?

PREDICTION Which object would have the greatest coefficient of rolling friction between itself and the carpet floor? Why? Justify your prediction.

Investigative plan Determine the procedures with which we can obtain the values needed in the knowledge probe which in turn will answer the QUESTION. Material list: ball, scale, ramp, stopwatch, meter stick, tape, carpeted area, pencil and paper, calculator Procedure: 1. Gather the materials. 2. Set up the ramp on the carpet 10 inches tall. 3. Release the ball down the ramp 4. Time the ball from when it touches carpet to when it stops. 5. Measure the displacement from the bottom of the ramp to where it stops. 6. Repeat the process 3 times, if the data is consistent. More if needed. 7. Record the data on the paper. 8.

OBSERVATION What values are measured? How many times do we repeat the trials? Object: Tennis Ball displacement time Trial 1 Trial 2 Trial 3 Trial 4 Trial 5

Data analysis What information can be derived from the observation? Object: Tennis Ball displacement time Initial velocity acceleration Trial 1 Trial 2 Trial 3 Trial 4

EVALUATION Using the acceleration that was calculated rom the data analysis, determine the coefficient of friction. Object: Tennis Ball displacement time Initial velocity acceleration Coefficient m Trial 1 Trial 2 Trial 3 Trial 4

EXPLANATION From the evaluation, ______________ has the greatest rolling coefficient of friction. Offer reasons why the object has the greatest rolling friction. 1. 2. 3. 4.