“You’re losing weight!” The mass of measurement
Where’s the summer going? Some of your kids are already back at school and some of you have a couple more weeks to while away. If you’re stuck for something to do, Joanne has some fun measurement experiments.
By Joanne Arcand
I learned pretty fast that the reply to “you’re losing weight” is not to respond by stating I’ve actually lost mass, but to say “Thank you” instead. Sometimes, it’s best to save the math lessons for a younger audience.
Like today, it’s a rainy day and the boys and I are playing with balloons. It reminded me of one of my favorite “wow” moments with the six-year-old mind.
“Man, you’re strong,” I say.
“Yep,” says G as he flexes his little six year old bicep, “I work out.”
“I can tell,” (giving the obligatory squeeze of the kiddie muscle), “you have a tonne of air pushing down on you all the time. That’s the weight of a small car.”
(A warning to those of you that might want to let the kid in on this secret - next time you’re in a mall, you may be hearing, “Mo-om! I’m sooooo tired, this air weighs a TONNE!”)
The air really does push down on us at about 10 000 kilograms per square meter. Thankfully, the air pushes in all directions, so there’s enough air pushing up that we don’t collapse like Wile E. Coyote when that anvil fell on his head. Here are a couple of other neat things to do with mass and weight.
Air really does have weight
Because all matter has mass, and air is a type of matter, air has mass which when combined with gravity means that air has weight. You can see this with a simple experiment.
Blow up two balloons, tie them and attach them to opposite ends of a straw with short pieces of string.
Using tape, attach another string to the middle of the straw so that you can hold the straw pretty much horizontal by holding onto the string. The balloons should hang below the straw (if they don’t, call 911, your lungs are filled with helium). Once the straw is horizontal and stationary, pop a balloon. The mass of the balloon should stay attached to the straw, but the air will (of course) escape. Talk about why the straw is no longer horizontal- the balloon with the air in it is heavier than the popped balloon. Air has mass and weight.
Make a spring scale
Go to a grocery store and drive the germaphobes crazy by finding fruits or vegetables that have different masses. Don’t get too heavy, this spring scale won’t be able to weigh a watermelon. Try to find fruits or vegetables that weigh exactly 1 gram, 2 grams, 5 grams, 10 grams, 50 grams, and so on. (For the American friends: 1 ounce, 2 ounces…you get the idea).
It’s like a scavenger hunt for food geeks. Write the weight of each item down so you don’t forget, pay for your groceries, and head on home. You’ll also need an elastic band about a ¼ inch (1/2 centimeter) thick and a small, lightweight, pail (I used an empty ice cream container; go ahead and get the Ben and Jerry’s! It’s for science!).
Tape a long strip of paper (I used a newspaper) to the edge of the table so that it hangs down. Attach one end of the elastic to the pail, the other end to the table (I forgot to say you might need duct tape too). As you add the fruits or vegetables, the elastic should stretch and you can mark the height of the pail on the paper. If it doesn’t react with your fruit, use a skinnier elastic.
Once you have all your markings, try a little mass-addition. Which two fruits will make the scale show 10 grams? Which four fruits will still be less mass than an orange? How much more mass will I have if I eat this entire fruit salad?
Speaking of which, time to eat!
Joanne Arcand is trying to juggle her role as a math teacher with her other life as mom of twin boys. She lives in Oakville, Ontario.
