I am looking at data used in a project to get the velocity and acceleration of a CME (Coronal Mass Ejection). I understand how the velocity was calculated, and for the acceleration, I get the v2-v1 part of the formula for acceleration that was used (ex. 306.5-331.2), but what time intervals (t2-t1) were used to calculate the accelerations?
The average velocity in the interval 8:05 to 8:36 is 331.2. So, use $v_1=$ 331.2 at $t_1=$ 08:20:30 under the assumption that acceleration is constant.
The average velocity between 8:36 and 9:27 is $v_2=$ 306.5, so use $t_2=$ 9:01:30
Acceleration is $(306.5-331.3)/(41\times60)=-0.01\ $km/s$^2$.
The same calculation gives me $0.029\ $km/s$^2$ and $-0.038\ $km/s$^2$.
Is this just arithmetic error on the first value (using 51m instead of 41m), a small rounding issue on the second and the third I agree with.
Other than that, then some unstated alternative interpolation scheme has been used.