“AMA” means more than “ask me anything”

The very first textbook chapter I edited (way back in 2008!) was on work and machines, so I have a soft spot for the topic. It’s also the focus of the “Science Playground” exhibit at the science museum I work for (and no, I will never, ever tire of the phrase “the science museum I work for”.)

There are lots of things to push and pull, and it’s a ton of fun interacting with guests who are lifting 550 pounds for the first time. It’s made me nostalgic for my textbook days, so I thought I’d summarize some of the key concepts and formulas here.

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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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Love is a “shocking” sensation

In honor of the SigFig’s birthday, today’s post is about the moment I knew we really had something special.

It is, unsurprisingly, science-related.

Several years ago, we were walking along the waterfront and paused to rest on a high-backed plastic bench. I kissed him and felt a mild shock.

“You’re crackly. Discharge.”

Without missing a beat, he got up and touched his fingertip to a metal railing. He knew exactly what I meant and exactly what he had to do to rectify the situation.

And, just like that, I was hooked.

So what was going on here? It’s all about the electrons.

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“Torque” isn’t just a terrible movie from 2004…

…it’s also an important concept that many of my physics students have studied recently.

Conceptually, torque is the quantity required to make an object rotate around a given point. I’m being very careful to avoid phrases like “how hard you have to turn something”, because there are ways to increase your torque without increasing the force you’re applying.

Distance from the point the object is rotating around is also a factor, as evidenced by the device I found in my parents’ kitchen.

Screen Shot 2016-02-07 at 11.13.07 PM
This photo is from Amazon, but I think my parents got theirs from the kitchen supplies equivalent of an Avon rep.

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Come for the cat video, stay for the science…

This showed up in my Facebook feed the other day.

As I watched this video about six or seven times in a row, you know I couldn’t help but consider the physics behind the poor kitty’s plight. We’ve discussed how an object only changes its motion (starts moving, stops moving, changes speed, changes direction) if an overall force acts on it. When a cat jumps off the floor, what’s applying the force that allows her to start moving upward?

Oddly enough, the floor is.

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I can sense you coming closer…

The science museum that I volunteer at recently opened up the traveling math exhibit that I’ve been looking forward to for a while. One of the activities features a piece of equipment that, as a physics student/teacher, is near and dear to my heart: the motion sensor. As you walk towards and away from the sensor, it records how far away you are and plots this distance on a graph.

It’s a nifty setup that gets people thinking about how motion can be described both visually and mathematically, but it does raise the question: how does the sensor know how far away you are?

The explanation is best illustrated with a game of catch.

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Physics (not) by the numbers: work and energy

I tutor several physics students right now, and I find myself starting a lot of conversations with the phrase ‘let’s look at this conceptually for a second’. Don’t get me wrong, I love math, but sometimes we have to step away from the numbers and formulae and use our words.

Work and energy are good topics to tackle conceptually. Like many words, they have very specific meanings in physics that differ from the colloquial usage.

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