created 08/01/99

#
Chapter 11 Programming Exercises

## Exercise 1

Write a program that calculates the annual cost of running an appliance. The
program will ask the user for the cost per kilowatt-hour and the number of kilowatt-hours
the appliance uses in a year:

Enter cost per kilowatt-hour in cents
8.42
Enter kilowatt-hours used per year
653
Annual cost: 54.9826

Click here to go back to the main menu.

## Exercise 2

When a brick is dropped from a tower, it falls
faster and faster until it hits the earth.
The speed v is given by

v = (1/2) g t^{2}

Here v is the speed in feet per second, t is the time in seconds,
and g is 32.174.
Write a program that asks the user for the number of seconds and
then prints out the speed.

Enter the number of seconds
5.4
Speed of the brick: 469.092 feet per second

One hundred miles per hour is 146.67 feet per second. Use your program to
determine approximately how long it takes the brick to reach that speed.

Click here to go back to the main menu.

## Exercise 3

The base 2 logarithm of a number is defined by:

log_{2} X = n if 2^{n} = X

For example

log_{2} 32 = 5, because 2^{5} = 32

log_{2} 1024 = 10, because 2^{10} = 1024

Write a program that inputs a number and outputs its base 2 logarithm.
Use floating point input.
This problem would be easy, but the Math package does not have a base 2
logarithm method.
Instead you have to do this:

log_{2} X = (log_{e} X) / (log_{e} 2)

Here, `log`_{e} X

is the natural logarithm of X.
Use this function in the Java Math package:

Math.log( X )

When you use this, X must be a double.
Write the program so that the user can enter floating point numbers.

Enter a double:
998.65
Base 2 log of 998.65 is 9.963835330516641

Click here to go back to the main menu.

## Exercise 4

The *harmonic mean* of two numbers is given by:

H = 2 / ( 1/X + 1/Y )

This is sometimes more useful than the more usual average
of two numbers.
Write a program that inputs two numbers (as floating point)
and writes out both the usual average (the arithmetic mean)
and the harmonic mean.

Enter X:
12
Enter Y:
16
Arithmetic mean: 14.0
Harmonic mean: 13.714285714285715

Click here to go back to the main menu.