RipStik Deceleration
Acceleration is introduced by riding a RipStik up a slope while decelerating, turning around at the top of the slope, and then accelerating back downslope. Posts along the covered walkway provide timing points. Prior to going outside on Monday I sketched a graph on the board of what a time versus distance graph should look like if I rode with decreasing speed and then turn around and ride with increasing speed. The result is a roughly parabolic prediction. Note that negative velocity on a graph was also covered on Monday.
On Wednesday I asked the students if they got the shape I predicted, which they did. Then I spent Wednesday showing them that a change in speed per unit time can be calculated, generating what I explained would be called acceleration. The students had the table above and the graph on a handout as reference.
I built from the slope of the above is the velocity to the slope of the velocity versus time is the acceleration.
I then drew attention to the acceleration always being negative until the final post and what that meant, negative with a slope of zero.
The handout also had the above chart. This then builds into measuring the acceleration of gravity.
time (s) | split dist (cm) | distance (cm) | velocity (cm/s) | acceleration (cm/s²) | |
0 | 0 | 0 | |||
0.97 | 306 | 306 | 315.46 | Running | |
2.13 | 305 | 611 | 262.93 | -45.29 | Avg Acc |
3.69 | 307 | 918 | 196.79 | -42.39 | -44 |
6.72 | 316 | 1234 | 104.29 | -30.53 | -39 |
10 | -316 | 918 | -96.34 | -61.17 | -45 |
11.82 | -307 | 611 | -168.68 | -39.75 | -44 |
13.07 | -305 | 306 | -244.00 | -60.25 | -47 |
14.69 | -306 | 0 | -188.89 | 34.02 | -35 |
Graphing the time versus the distance (third column) provides speed information from the slope. The students were given this as homework.
I built from the slope of the above is the velocity to the slope of the velocity versus time is the acceleration.
I then drew attention to the acceleration always being negative until the final post and what that meant, negative with a slope of zero.
The handout also had the above chart. This then builds into measuring the acceleration of gravity.
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