Two Dumb Questions That Sometimes Keep Me Up At Night

Factual Questions
1

Question 1:

 A six-sided object where each side is a square is called a cube.
 A six-sided object made with four rectangles and a square on each end is called a             ? 
 (I usually use the term "refrigerator shaped" but that's kind of wordy.)

Question 2:

 E=mc squared, right? Cool.
 What numbers can I plug into this to actually do the math?
 For example, I read somewhere (how's that for citing your sources?) that the "m" stood for mass in grams.

Assuming that that’s correct, if I have one gram of matter then the equation looks like this: E=1c2, right?
What units of measurement do I use for E and C?

2

The only thing required is that you be consistent in your units.

For example, in the English system energy, E, is in foot-pounds. Mass is in slugs which has the units of lb-sec[sup]2[/sup]/ft and c is in ft/sec. So on the right side of the equation the units work out as:

lb-sec[sup]2[/sup]/ft*ft[sup]2[/sup]/sec[sup]2[/sup] and if you go through the cancellation it all works out to ft-lb.

The same thing happens in metric. If you use meters and kg for distance and mass the energy is in joules.

If you use cm and grams the energy is in ergs.

3

The answer to the first one is PRISM.

4

I remember from geometry class calling it a rectangular prism. I suppose calling it an oblong hexahedron would suffice as well.

5

I think in order to specify that the shapes on the ends are squares, you’d have to call it a square prism. And in order to specify that the sides are right quadrilaterals (rectangles), you’d have to call it a right square prism.

6

Close, but no refrigerator. That would be a five sided object made of rectangles and triangles, wouldn’t it?

David, I’ve never heard of ‘slugs’ as a unit of measurement before. Thanks for introducing me to a new term, I can’t wait to use it in a sentence.
How do I measure ergs? How many ergs is my twenty watt desk lamp putting out?

7

A watt is a unit of power, which is energy / time. So, a 20-watt bulb uses up 20 joules / sec. One joule = 10,000,000 ergs (or, if you prefer, an erg is 1/10,000,000 joule). So, a 20-watt bulb uses 200,000,000 ergs/sec.

That’s a lot of ergs.

By the way, an erg is also known as a “dyne-centimeter”, where 1 dyne = 1 g*cm/s[sup]2[/sup].

8

It’s a special case for a rectangular parallelepiped of dimensions a x b x c, with a = b. I don’t know if there is a special term for it beyond that. It can also be called a Cuboid.

9

The slug as a unit of mass comes from F = m*a. Forces are in pounds, mass in slugs and acceleration in ft/sec[sup]2[/sup].

solve for m = F/a and make F = 1 lb and a = 1 ft/sec[sup]2[/sup]. then the mass is 1 slug. The units are:

lb/(ft/sec[sup]2[/sup]) = lb-sec[sup]2[/sup]/ft.

How do I find the mass if I know the weight? Well the weight is the force of gravity and if a weight W falls in a gravitational field the acceleration is g. On the surface of the earth that is 32.17 ft/sec[sup]2[/sup]. Again using m = F/a, F is W and a is g.

m = W/g.

So to find the mass in slugs, divide the weight by the acceleration of gravity.

PS - I think that’s true for both “right hand” and “left hand” weights.

10

I concur with Genseric. And a shape which is elongated with triangular ends was taught to me to be a triangular prism, as opposed to a pyramid.