# Uncertainty Question

Discussion in 'Homework Help' started by KaiL, Jan 18, 2015.

1. ### KaiL Thread Starter Member

Aug 30, 2014
69
0
To find the acceleration of a glider moving down a sloping air track, you measure its
velocities (v1 and v2) at two points and the time t it takes between them, as follows:
v1 = 0.210 +/- 0.05m/s
v2 = 0.850 +/- 0.05m/s
t = 8 +/- 0.1 second
What should you report for the acceleration, a = (v2 - v1)/ t and its uncertainty?

How to find the uncertainty in this question?
acceleration, a = (v2 - v1)/ t = 0.08 m/s^2 but how do I find the uncertainty?

2. ### WBahn Moderator

Mar 31, 2012
24,553
7,691
Have you done propagation of errors?

Are your uncertainties in each measurement assumed to be Gaussian (i.e., normally distributed)?

Are these uncertainties the standard deviation of the measurement error?

Are the uncertainties in each measurement assumed to be independent (meaning that if your error in v1 happens to be such that your measurement is too fast, that your measurement in v2 is just as likely to be too fast as too slow instead of it being a case where your measurement technique tends to result in measurements that are too fast)?