Introduction and Error Analysis - Examples & Applications
This section explores practical examples covering mathematical modeling, error definitions (true, relative, and approximate), round-off and truncation errors, Taylor Series expansions, and error propagation.
Mathematical Modeling
A mathematical model formulates physical principles into an equation. The classic example is Newton's Second Law applied to a falling parachutist.
Basic: Terminal Velocity of a Parachutist
A parachutist with a mass of jumps out of a stationary hot air balloon. The drag coefficient is . Compute velocity prior to opening the chute at . Acceleration due to gravity is .
The analytical solution for velocity is:
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0 of 3 Steps CompletedIntermediate: Radioactive Decay Modeling
The rate of decay of a radioactive substance is proportional to the amount of substance present: . Given an initial amount and a decay constant , compute the amount remaining after using the exact analytical model.
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0 of 2 Steps CompletedAdvanced: Unforced Spring-Mass System
An unforced, undamped spring-mass system is modeled by . Given , , initial displacement , and initial velocity , determine the displacement at .
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0 of 3 Steps CompletedAccuracy, Precision, and Significant Digits
Accuracy refers to how closely a computed or measured value agrees with the true value. Precision refers to how closely individual computed or measured values agree with each other. The concept of significant digits is crucial in numerical methods to quantify precision.
Case Study 1: Bridge Deflection Measurements
An engineering team measures the mid-span deflection of a bridge under a test load. The true theoretical deflection is .
Team A's measurements:
Team B's measurements:
Analyze the accuracy and precision of both teams.
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0 of 2 Steps CompletedCase Study 2: Concrete Compressive Strength Testing
Three batches of concrete cylinders are tested for their 28-day compressive strength. The design target (true value) is .
Batch X: Batch Y: Batch Z:
Evaluate the accuracy and precision.
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0 of 1 Steps CompletedError Definitions
Basic: True and Relative Error
The true value of is approximately . A student estimates as . Calculate the true error and true percent relative error.
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0 of 3 Steps CompletedIntermediate: True and Relative Error Calculation
The derivative of a function at is true value . A numerical method estimates the derivative to be . Calculate the true error and the true percent relative error.
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0 of 3 Steps CompletedAdvanced: Approximate Percent Relative Error
In an iterative numerical method to find a root, the estimate in iteration 2 is , and the estimate in iteration 3 is . Calculate the approximate percent relative error.
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0 of 2 Steps CompletedTaylor Series and Truncation Errors
Truncation errors occur when exact mathematical formulations are replaced by approximations, such as truncating a Taylor series after a finite number of terms.
Basic: Zero-Order Taylor Series
Approximate at using a zero-order Taylor series based at . True value is .
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0 of 2 Steps CompletedIntermediate: Second-Order Taylor Series
Approximate at using a second-order Taylor series based at . True value is .
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0 of 3 Steps CompletedAdvanced: Taylor Series Approximation
Approximate the function at using a zero-order and first-order Taylor series expansion based on the base point . Compute the true percent relative error for each approximation.
Given: True value
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0 of 2 Steps CompletedError Propagation
Error propagation deals with how errors in individual variables or measurements combine to produce error in a calculated result.
Basic: Error Propagation in Addition
Given two measurements with their associated estimated errors:
Determine the maximum possible error in the sum .
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0 of 2 Steps CompletedIntermediate: Error Propagation in Multiplication
Given the sides of a rectangle and , find the maximum error in the calculated area .
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0 of 3 Steps CompletedAdvanced: General Error Propagation Formula
The deflection of a beam is given by . If the measured force is with an error of , and the length is with an error of . Assume and are exact, where . Use the general first-order error propagation formula to estimate the maximum error in deflection.