While moving to Pluto would cause drastic “weight loss”…

…it won’t do a thing for your mass.

The science museum where I work (<3!) has a scale that displays how much you would weigh on various astronomical bodies. I was standing nearby when a family from the UK stepped on, and one of the mothers expressed mild dismay that the display didn’t show both pounds and kilograms. I just had to jump in.

The display would be very uninformative if it displayed kilograms, as the number would be the same for every single planet. While pounds are a unit of force (like the Newton), kilograms are a measure of mass, not weight.

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…don’t worry, it’s perfectly normal.

AKA Freebody Diagrams, Part Two.

For a definition of/conceptual take on freebody diagrams and the forces within them, make sure you check out Part One, then head on back here to plug in the numbers.

Let’s begin by reviewing our basic freebody diagram from last time- but with one small change.

Click to enlarge.

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The science of physical attraction

First off, this post is probably not about what you think it’s about.

Second off, even if you are alone on Valentine’s Day, take comfort in the fact that it doesn’t mean that no one is attracted to you. In fact, everyone is attracted to you! Every THING is attracted to you.

Gravitationally, that is.

We’re used to defining gravity as the force that holds us down on Earth, but there’s actually a gravitational force between any two objects that have mass. There’s an attractive force between you and Earth, you and the moon, you and your good-looking neighbor…so why are we always pulled toward Earth and not our neighbors?

The answer can be explained mathematically.


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Getting my daily dose of science

From the time I began college up until my relocation to suburbia about a year ago, science was my bread and butter: I was a physics major, then a high school physics teacher, then a science textbook editor. Now that I work as a math tutor and humor website moderator, I have to get all of my science cravings fulfilled on my own time.

Since science really is all around us, coming up with Ideas for Doing Science isn’t difficult at all. Sometimes I look at the neighborhood pool across the street and want to mix in a large quantity of cornstarch. A lesson in non-Newtonian fluids and an absolute blast to run across, but such large-scale Random Acts of Science are often bad ideas (unless you’re a Mythbuster, which is pretty much my dream job). So I have to get my geek on in more manageable ways.

It doesn’t get much more manageable than a slinky. Slinkys move the way they do because of the interaction between two forces: gravity and the restoring (“springy”) force of the spring. When you push a slinky down a flight of stairs, gravity causes one end to fall to the next step. This stretches the spring out. The restoring force pulls the other end down to restore the spring to its natural, unstretched state. However, while the spring is restoring to its natural state, gravity is still acting. Gravity pulls the slinky down to the next step and the cycle repeats.

What if we add a third force to this system: the buoyant (“floaty”) force? In other words, how does a Slinky move underwater?

Good thing I have that pool across the street. I’ll report my findings in a future post.