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Lære Analyzing Real-World Motion Data | Kinematics and Motion
Python for Physics Students

bookAnalyzing Real-World Motion Data

To work with real-world motion data in Python, you first need to import your data, clean it, and process it so it can be analyzed. Typically, you collect position and time measurements, often stored in a CSV file. Start by loading this data into Python using libraries such as pandas or numpy. Data cleaning is a crucial step: you might need to remove duplicate entries, handle missing values, or correct obvious errors in the measurements. Once the data is tidy, you can process it to calculate quantities like velocity or acceleration, which are essential for understanding the object's motion.

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import numpy as np import matplotlib.pyplot as plt import pandas as pd # Simulate position-time data for an object in motion (e.g., constant acceleration) np.random.seed(0) num_points = 15 time = np.linspace(0, 5, num_points) # Simulate motion: s = ut + 0.5at^2 (u=0.5 m/s, a=1.2 m/s^2) position = 0.5 * time + 0.5 * 1.2 * time**2 # Add small random noise to simulate measurement error position += np.random.normal(0, 0.1, size=position.shape) # Save the simulated data to CSV sim_data = pd.DataFrame({'time': time, 'position': position}) sim_data.to_csv('motion_data.csv', index=False) # Load position-time data from the CSV file # CSV has columns: time (s), position (m) data = np.genfromtxt('motion_data.csv', delimiter=',', skip_header=1) time = data[:, 0] position = data[:, 1] # Compute velocity using finite differences velocity = np.diff(position) / np.diff(time) velocity_time = (time[:-1] + time[1:]) / 2 # Midpoints for velocity plot # Plot position vs. time and velocity vs. time plt.figure(figsize=(10, 4)) plt.subplot(1, 2, 1) plt.plot(time, position, 'o-', label='Position') plt.xlabel('Time (s)') plt.ylabel('Position (m)') plt.title('Position vs. Time') plt.legend() plt.subplot(1, 2, 2) plt.plot(velocity_time, velocity, 'o-', color='orange', label='Velocity') plt.xlabel('Time (s)') plt.ylabel('Velocity (m/s)') plt.title('Velocity vs. Time') plt.legend() plt.tight_layout() plt.show()
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Once you have plotted your position and velocity data, you can begin to interpret the results. Look for trends, such as whether the object moves with constant velocity or accelerates. Anomalies—like sudden jumps or drops in the data—could indicate measurement errors, data entry mistakes, or unexpected physical effects. Careful inspection of the plots helps you decide if further cleaning or corrections are needed, and also provides insight into the physical behavior of the system you are studying.

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import numpy as np import matplotlib.pyplot as plt # Assume time and position arrays are already loaded as in the previous example # Fit a linear model: position = slope * time + intercept coefficients = np.polyfit(time, position, 1) slope, intercept = coefficients # Generate fitted line position_fit = slope * time + intercept # Plot original data and fitted line plt.plot(time, position, 'o', label='Measured Position') plt.plot(time, position_fit, '-', label='Linear Fit') plt.xlabel('Time (s)') plt.ylabel('Position (m)') plt.title('Position vs. Time with Linear Fit') plt.legend() plt.show()
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Fitting a linear model to your position versus time data allows you to quantify the motion more precisely. The slope of the fitted line represents the average velocity of the object if the motion is uniform. If the data points closely follow the straight line, it suggests the object moved with nearly constant velocity. Deviations from the line may indicate acceleration, deceleration, or measurement inconsistencies.

1. Why is data cleaning important before analyzing experimental results?

2. What does the slope of the fitted line represent in a position vs. time graph?

question mark

Why is data cleaning important before analyzing experimental results?

Select the correct answer

question mark

What does the slope of the fitted line represent in a position vs. time graph?

Select the correct answer

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Seksjon 1. Kapittel 6

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bookAnalyzing Real-World Motion Data

Sveip for å vise menyen

To work with real-world motion data in Python, you first need to import your data, clean it, and process it so it can be analyzed. Typically, you collect position and time measurements, often stored in a CSV file. Start by loading this data into Python using libraries such as pandas or numpy. Data cleaning is a crucial step: you might need to remove duplicate entries, handle missing values, or correct obvious errors in the measurements. Once the data is tidy, you can process it to calculate quantities like velocity or acceleration, which are essential for understanding the object's motion.

12345678910111213141516171819202122232425262728293031323334353637383940414243444546
import numpy as np import matplotlib.pyplot as plt import pandas as pd # Simulate position-time data for an object in motion (e.g., constant acceleration) np.random.seed(0) num_points = 15 time = np.linspace(0, 5, num_points) # Simulate motion: s = ut + 0.5at^2 (u=0.5 m/s, a=1.2 m/s^2) position = 0.5 * time + 0.5 * 1.2 * time**2 # Add small random noise to simulate measurement error position += np.random.normal(0, 0.1, size=position.shape) # Save the simulated data to CSV sim_data = pd.DataFrame({'time': time, 'position': position}) sim_data.to_csv('motion_data.csv', index=False) # Load position-time data from the CSV file # CSV has columns: time (s), position (m) data = np.genfromtxt('motion_data.csv', delimiter=',', skip_header=1) time = data[:, 0] position = data[:, 1] # Compute velocity using finite differences velocity = np.diff(position) / np.diff(time) velocity_time = (time[:-1] + time[1:]) / 2 # Midpoints for velocity plot # Plot position vs. time and velocity vs. time plt.figure(figsize=(10, 4)) plt.subplot(1, 2, 1) plt.plot(time, position, 'o-', label='Position') plt.xlabel('Time (s)') plt.ylabel('Position (m)') plt.title('Position vs. Time') plt.legend() plt.subplot(1, 2, 2) plt.plot(velocity_time, velocity, 'o-', color='orange', label='Velocity') plt.xlabel('Time (s)') plt.ylabel('Velocity (m/s)') plt.title('Velocity vs. Time') plt.legend() plt.tight_layout() plt.show()
copy

Once you have plotted your position and velocity data, you can begin to interpret the results. Look for trends, such as whether the object moves with constant velocity or accelerates. Anomalies—like sudden jumps or drops in the data—could indicate measurement errors, data entry mistakes, or unexpected physical effects. Careful inspection of the plots helps you decide if further cleaning or corrections are needed, and also provides insight into the physical behavior of the system you are studying.

1234567891011121314151617181920
import numpy as np import matplotlib.pyplot as plt # Assume time and position arrays are already loaded as in the previous example # Fit a linear model: position = slope * time + intercept coefficients = np.polyfit(time, position, 1) slope, intercept = coefficients # Generate fitted line position_fit = slope * time + intercept # Plot original data and fitted line plt.plot(time, position, 'o', label='Measured Position') plt.plot(time, position_fit, '-', label='Linear Fit') plt.xlabel('Time (s)') plt.ylabel('Position (m)') plt.title('Position vs. Time with Linear Fit') plt.legend() plt.show()
copy

Fitting a linear model to your position versus time data allows you to quantify the motion more precisely. The slope of the fitted line represents the average velocity of the object if the motion is uniform. If the data points closely follow the straight line, it suggests the object moved with nearly constant velocity. Deviations from the line may indicate acceleration, deceleration, or measurement inconsistencies.

1. Why is data cleaning important before analyzing experimental results?

2. What does the slope of the fitted line represent in a position vs. time graph?

question mark

Why is data cleaning important before analyzing experimental results?

Select the correct answer

question mark

What does the slope of the fitted line represent in a position vs. time graph?

Select the correct answer

Alt var klart?

Hvordan kan vi forbedre det?

Takk for tilbakemeldingene dine!

Seksjon 1. Kapittel 6
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