How to Use Google’s Calculator in a Physics Class

[This is a guest post by David L. Morgan, who is an assistant professor of physics and astronomy at Eugene Lang College in Manhattan. -- JBJ]

One of the first things I teach the students in my physics and astronomy classes is to learn how to use Google’s built-in calculator function. If you type something into Google’s search field that Google recognizes as a mathematical expression, it automatically performs as a calculator instead of merely searching for that expression. For example, typing…

6 – 2

2^2

sqrt(16)

will each cause Google to respond with the answer “4.” The syntax is the same as most computer languages: + and – for addition and subtraction, * and / for multiplication and division, ^ for exponentiation and sqrt() for square roots. Everything you would be able to do on a scientific calculator, Google’s calculator will understand – sin, cos, ln, etc.

But the calculator does more than just pure math: it also handles units in mathematical expressions, which makes it particularly useful for doing calculations in a physics class. Unit conversions are the place where I use Google’s calculator most often. The word that clues in the calculator that you want to do a unit conversion is “in”  - as in “in seconds”, “in miles” or “in mph”. Jumping from British to SI units or from some combination of units as strange as calories per week to horsepower is a simple one-step process. For example, try typing the following into Google…

14 billion years in seconds

20 light years in feet

2000 kilocalories per day in Watts

1.5 cups in tbsp

speed of light in miles per hour

(If you ask it for some incompatible transformation like “15 pounds in inches” it will disregard the statement as a mathematical one and simply revert to searching the internet for those words.)

It can also handle units within calculations and express the answer in the units of your choice.

65 miles/3 hours in m/s

100 grams * 10 m/s^2 in pounds

1.5 atm * 4L in ergs

Common constants in physics such as G, c, or h can be entered simply by typing the abbreviation. Masses of common astronomical objects can be accessed by typing m_earth or m_sun or m_jupiter. So if I want to calculate the gravitational force between the Earth and Sun using Newton’s Law of Gravitation, I can simply enter Gm_earthm_sun/(1 AU)^2

It takes a little trial and error to figure out what Google’ built-in calculator knows and doesn’t know, since there isn’t really a “manual” with a comprehensive list of constants and units. The page at http://www.google.com/help/calculator.html is a start, but doesn’t begin to scratch the surface. But if you need to do more than add and subtract (but less than the all-out Mathematica engine provided by Wolfram Alpha) and you keep the Google search field handy anyway, Google’s calculator could save you reaching for your beat up old Casio or HP a few times a day.

Image by flickr user teriyaki tofu / CC licensed