# Homework Help: AP physics b free response questions

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1. Sep 15, 2011

### le123

1. The problem statement, all variables and given/known data
A world-class runner can complete a 100 m dash in about 10 s. Past studies have shown that runners in such a race accelerate uniformly for a time tu and then run at constant speed for the remainder of the race. A world-class runner is visiting your physics class. You are to develop a procedure that will allow you to determine the uniform acceleration au and an approximate value of tu for the runner in a 100 m dash. By necessity your experiment will be done on a straight track and include your whole class of eleven students.

c. Outline the process of data analysis, including how you will identify the portion of the race that has uniform acceleration, and how you would calculate the uniform acceleration.

2. Relevant equations
x=1/2 a(t)^2

3. The attempt at a solution

I tried using the equation above, but I'm not exactly sure how to explain the process of data analysis or how to identify the portion that has uniform acceleration

I'm not actually supposed to solve the equation, I just have to describe how you would go about solving it by using a description defining all variables being used, description showing how the needed variables (acceleration or final velocity) will be determined, and a transformation of the description into equation form

The thing that I am having trouble with is explaining my answer. I have to include all of the information above^^^

Last edited: Sep 15, 2011
2. Sep 15, 2011

### Gordanier

Hmm, is that all the information you are given?

You could find an average acceleration until the race is over, or an average velocity, but I don't think you can find what you are asking based on just the above information.

Maybe I'm wrong and missing something or overcomplicating it, but check to see if anything else was given.

3. Sep 15, 2011

### diazona

This is not a "normal" physics problem - you don't answer this question by plugging things into equations and solving for them. They're testing your knowledge of experimental design. So your answer should address things like what quantities you'll need to measure, how and when you will measure them, and how you can use the values you measure to determine the desired result.

You should probably also include some sort of error analysis: try to identify the factors that could introduce inaccuracies into your measurements, and comment on how those inaccuracies might affect the final result.

4. Sep 15, 2011

### Chrisas

"include whole class of 11 students."

I think this is a key statement. I would spread the students out along the track with synchronized watches. Then each student would write down the time that the runner passed them.

If you do that, can you describe how you would use the times to come up with the acceleration time and the amount of acceleration?

5. Sep 15, 2011

### Gordanier

EDIT:

Doh, I misread what he was required to do. My mistake.

Cheers