Physics 2215 Minilab 1 Measurement and Estimation Purpose

Physics 2215 Minilab 1: Measurement and Estimation Purpose • Gain experience in calculating and propagating errors associated with measurements. • Gain experience in performing rough estimations.

Physics 2215 Minilab 1: Measurement and Estimation Finding Uncertainties from Repeated Measurements Repeated measurements can give you different results due to • Object variation (e. g. , the width of a table may be different at different positions, or it may vary with temperature or moisture in the air). • Measurement device or procedure may create scatter in the result. Take many (5 or more) measurements and calculate the mean.

Physics 2215 Minilab 1: Measurement and Estimation Mean Standard Deviation A measure of how far individual data scatter. Standard Deviation of the Mean This is the uncertainty/error in the mean value. Result

Physics 2215 Minilab 1: Measurement and Estimation Error Propagation A general physics formula…. . And some measurement with uncertainties…. . Plug in x, y, z…. . to get value of “ f ” Calculate uncertainty in “ f “: Result

Physics 2215 Minilab 1: Measurement and Estimations…an example How many (NT) new car tires are bought in Utah every year? P: Population: 2 Million A: % that are adults and drive a car: 60% M: Number of miles driven per adult per year: 15000 miles N: Number of tires per car: 4 L: Number of miles during life of tire: 45000 miles

Physics 2215 Minilab 1: Measurement and Estimation What we will look at closely when grading… Ø Did you make reasonable estimations/calculations of uncertainties? Ø Did you report significant figures correctly? Ø Did you propagate your errors without mistakes? Ø When you performed an estimation, did you perform logical reasoning to arrive at your estimate.