01 Class Activity: Review Python

Purpose

Write a Python program that gets input from a user, uses variables, performs arithmetic using the math module, and displays results for the user to see.

Problem Statement

The time in seconds that a pendulum takes to swing back and forth once is given by this formula:

t = 2π

√

h

9.81

t is the time in seconds,
π is the constant PI, which is the ratio of the circumference of a circle divided by its diameter (use math.pi),
h is the length of the pendulum in meters.

Activity

Write a program named pendulum.py that prompts a user to enter the length of a pendulum in meters and then computes and prints the time in seconds that it takes for that pendulum to swing back and forth. To start your program, copy and paste the following code into your program and use it as an outline as you write code. Note that in a Python program, a triple quoted string at the top of the file acts as a comment for the entire program.

"""
The time in seconds that a pendulum takes to swing back and
forth once is given by this formula:
             ____
            / h
    t = 2π / ----
          √  9.81

t is the time in seconds,
π is the constant PI, which is the ratio of the circumference
    of a circle divided by its diameter (use math.pi),
h is the length of the pendulum in meters.

Write a program that prompts a user to enter the length of a
pendulum in meters and then computes and prints the time in
seconds that it takes for that pendulum to swing back and forth.
"""

Helpful Documentation

The preparation content for this lesson explains how to write code to do the following:
- Get input from a user
- Convert user input from a string to a number
- Calculate results
- Display results for the user to see
The Python math module contains mathematical constants and functions including math.pi and math.sqrt().

Testing Procedure

Verify that your program works correctly by following each step in this testing procedure:

Run your program and enter the input shown below. Ensure that your program’s output matches the output below.
```
> python pendulum.py
Length of pendulum (meters): 1.5
Time (seconds): 2.46
```

Sample Solution

Please work diligently with your class to complete this activity. After class is over, please compare your solution to the sample solution. Please do not look at the sample solution until you have either finished the program or diligently worked with your class.

Ponder

During this assignment, you wrote a Python program that gets input from a user, uses variables, performs arithmetic, and displays results for the user to see. Because you should have learned how to write this type of program in CSE 110, this assignment should have been fairly easy for you. If this assignment was difficult for you, you should review the concepts from CSE 110 and the programs that you wrote in that course.