1. The problem statement, all variables and given/known data: The expressions you obtained for acceleration and drainage time (equations 3 and 4 in the manual) both contain the following factor or something equivalent: (D/d)^4-1 In the lab, we will be dealing with a bottle with a diameter around 9 cm. A typical diameter of the drainage hole is 8 mm. With these numbers, what is the maximum error that we introduce in the expression above if we use the approximation: (D/d)^4-1 ~ (D/d)^4 This is a small error compared to the uncertainties in the lab (the motion detector alone has a resolution of 1 mm. Since we will be measuring distances of the order of 20 cm, this is already a 0.5% uncertainty.) 2. Relevant equations This question makes NO sense to me. I don't get the point of the approximation equation. 3. The attempt at a solution Wouldn't the maximum error just be 9cm/8mm or 9/.08 = 112.5 OR would it be .08/9 = .008 or 2/225? I've tried both of these answers but the program didn't accept either. What am I doing wrong? How am I supposed to use the approximation equation listed in the question??? Thank you sooooo much, this is due tomorrow night so I'm allowed to enter the lab/participate on Monday.