Welcome!

Welcome to Dr. B's Science Lab, a non-commercial resource for up-to-date and accurate science content, activities, and projects. Explore a different topic every month, and get the whole family involved in learning and experimenting! Just be sure to follow the directions exactly and pay attention to any safety information given.

If you would like to receive email updates whenever new content is added to Dr. B's Science Lab, submit your address in the "Follow by Email" link at left. Your email address will not be used for any other purpose.



Wednesday, August 3, 2011

Payload

So, helium rises because it's less dense than air, but you know that there's a limit to how much weight a helium balloon can lift. Obviously, it can lift the weight of the actual balloon and the string, but it won't lift you up into the sky (which is probably a good thing!). How much weight can a helium balloon lift? And could you gather enough helium balloons to lift yourself? Here's a experiment to try and some calculations that will let you figure that out!

What You'll Need:
Helium-filled balloon with string
Standard-sized metal paper clips (about 1-1/2" long)

Do this experiment indoors! Make a loop in the end of the string; the balloon should still float. Then attach one paper clip to the loop. Does the balloon still float? Keep attaching paper clips until the balloon can no longer lift its payload (the amount of weight that a device can lift). How many paper clips did it take?

Now for some math! We're going to do these calculations in the metric system because it's easier, and it's what scientists use! The weight of one standard-sized metal paper clip is about 0.5 grams. Grab a calculator and multiply the largest number of paper clips the balloon could lift by 0.5 grams. This tells you the total weight that the balloon can lift. So, if the balloon payload was 3 clips, that gives you 4.5 grams.

How much do you weigh? If you know your weight in pounds, multiply that number by 454 (the number of grams in a pound). If you know your weight in kilograms, multiply by 1000 (the number of grams in a kilogram). Let's say you weigh 60 pounds - that's 27,240 grams. Or, if you're 18 kilograms, that's 18,000 grams. Don't worry about how big those numbers are - grams are really small!

That's all the information you need to figure out how many balloons it would take to lift you off the ground. Can you do the calculation on your own? Think about it, and read the next paragraph only if you need help.

In the example above, the balloon lifted 4.5 grams (your number may be different). You should be able to see that two balloons could lift 9.0 grams (2 x 4.5). How much weight could 10 balloons lift? The answer is 10 balloons x 4.5 grams/balloon = 45 grams. Now we'll ask the question in another way - how many balloons would it take to lift 45 grams (about one pound)? Wait, we already know that answer (10), but let's see how the calculation is done. You don't multiply in this case, you divide: 45 / 4.5 = 10. How many balloons are needed to lift 100 grams? The calculator shows 100 / 4.5 = 22.22222..., but we really can't have a fraction of a balloon, so we'll raise the number to 23. You're probably beginning to see that it will take a lot of balloons to lift you. The last calculation is up to you. Divide your weight (in grams) by the payload weight of your balloon, and you'll have your answer!

No comments:

Post a Comment