I need help for Part I. 472 SubmitMy AnswersGive Up Correct It is difficult to b

Question

I need help for Part I.

472

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Correct

It is difficult to be sure what frame, exactly, corresponds to any particular displacement–so, realistically, your results may differ from those of others. Meanwhile, in this particular problem, even a one-frame difference would result in a fairly large discrepancy when used in calculations.

To provide consistency for the remainder of the problem, let's assume that the ball reaches the 0.10-m mark in frame 474.

Part H

How many seconds does it take the blue ball to cover the distance 0.10 m? Remember that we agreed to assume that the motion begins in frame 130, and the 0.10-m mark is reached in frame 474.

Express your answer in seconds with three significant figures.

Hints

0.143

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Correct

Part I

According to your measurements, what is the average acceleration of the blue ball as it falls the first 0.10 m?

Express your answer in m/s2 with three significant figures.

Hints

0.001

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Information from the video=

Video text description for the Direct Measurement Video of Falling Through the Air

In this video, three different balls are held above the ground by ribbons: a blue foam ball with mass 3.15 grams; a small orange steel ball with mass 67.1 grams; and a large purple bowling ball with mass 5539 grams. A vertical scale, marked off in centimeters, is aligned with each ball, with the bottom of each ball at the 0-centimeter line at the beginning of the video. The video is shot at 2400 frames per second, so plays at 80 times slower than normal speed. A frame counter indicates the current frame.

At frame 130, someone cuts each ribbon at exactly the same time and the balls all start falling under the influence of gravity. At first, all the balls seem to move together, but it soon becomes clear that the blue ball takes longer to go the same distance as the others. The orange and purple balls both reach the 10-centimeter mark at around frame 472, while the blue ball takes two frames longer, reaching the 10-centimeter mark at frame 474. Later, the orange and purple balls both reach the 90-centimeter mark at around frame 1157, while the blue ball takes all the way until frame 1181 to reach 90 centimeters.

472

Explanation / Answer

x = distance travelled = 0.1 m

vo = initial velocity = 0 m/s

a = acceleration

t = time = 0.143 sec

using the equation

x = Vo t + (0.5) a t2

0.1 = 0 (0.143) + (0.5) (a) (0.143)2

a = 9.78 m/s2

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