A rolling ball moves from x_1 = 8.4 cm to x_2 = -4.2 cm during the time from t_1 = 3.0 s to t_2 = 6.1 s . What is its average velocity over this time interval?

This is Giancoli Answers with Mr. Dychko. To calculate the average velocity, we take the difference in position divided by the change in time. So at time t 2, it's at position negative 4.2 centimeters and at time t 1, it's at position 8.4 centimeters and so we take the difference between their positions— negative 4.2 centimeters minus 8.4— and divide by the change in time— t 2 is 6.1 seconds and t 1 is 3.0 seconds. Divide this top difference by the bottom difference and you end up with negative 4.1 meters per second is the average velocity.

COMMENTS

By joseotilio25 on Sun, 2/22/2015 - 5:25 PM

Why m/s if I have cm/s

By Mr. Dychko on Sun, 2/22/2015 - 10:12 PM

Hi joseotilio25, because... I made a typo! Thanks a lot for catching that. I've made a note above the video, and updated the quick answer. The units should be $\textrm{cm/s}$ , as you say.

Cheers,
Mr. Dychko

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A rolling ball moves from x1=8.4 cmx_1 = 8.4 \textrm{ cm}x1​=8.4 cm to x2=−4.2 cmx_2 = -4.2 \textrm{ cm}x2​=−4.2 cm during the time from t1=3.0 st_1 = 3.0 \textrm{ s}t1​=3.0 s to t2=6.1 st_2 = 6.1 \textrm{ s}t2​=6.1 s. What is its average velocity over this time interval?

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A rolling ball moves from $x_1 = 8.4 \textrm{ cm}$ to $x_2 = -4.2 \textrm{ cm}$ during the time from $t_1 = 3.0 \textrm{ s}$ to $t_2 = 6.1 \textrm{ s}$ . What is its average velocity over this time interval?