Blog three: Heads Up, We're Coming Down

"Talk to the hand."

This lunchbox part of a dramatic reenactment.

Pop quiz! What do you get when you combine my accident-prone friend, a metal lunch box, and a distracted high school student?

You get an announcement in the Daily Bulletin asking students to please stop putting things on the railing of second floor I-building.

Good times, man. Good times.

Alright, it wasn't really good times.

But, back to physics. The lunchbox was balanced on the railing while the absent-minded student was diddling about in her locker. She (while wearing her gigantic school-issued backpack) then backed up and it was all over bar the blood and out-freaking.

In other words, it was launched horizonally, which incidentally makes these numbers a lot easier to calculate!

There is no way this could possibly go wrong.

As we're all aware, the horizontal and vertical components of a vector may be treated separately. I have a tape measure, so let's get started.

We already know

initial vertical speed = 0 m/s

vertical acceleration = -9.8 m/s/s

and I went and found out that vertical displacement = -3.27 m

So now we can find out time because (say it with me, everybody!)

displacement = initial velocity*time + 0.5*acceleration*time*time

So time = 0.58 s

And we (and by "we" I mean "I," obviously) can then figure out the horizontal velocity using the same equation, because my tape measure says that the lunchbox went 0.80 m in the horizontal direction.

horizontal velocity = 1.38 m/s

Pretty good booty bump, yes?

And finally, we can find out the lunchbox's final vertical velocity (how fast it was going when it creamed her).

instantaneous velocity = initial velocity + acceleration*time

instantaneous vertical velocity = -5.73 m/s

She's going to want to put some ice on that.

PS: I used three pictures Ms C. Do I get, like, bonus points? 

Blog 2

C'mon, Ms. C, that's a boring title...

Please ignore the glow-in-the-dark dinosaurs. Thank you.

As you can see, my door is a rather dull dark brown. I try to liven it up with some decorations. (If it looks pitiful, that's because I'm in the middle of changing over the posters and stuff.) I found this really spiffy water color painting a while back, and decided to put it up. That's all well and good, except that the door is solid wood, and my parents might take badly to me putting things up using thumbtacks and a really big hammer. Instead, I've been using blue poster tack.

However, it isn't as sticky as I'd like, and sometimes the corners come unstuck, as you can see. When that happens, it's only a matter of time until the painting falls off entirely.  Sod's Law (also called Murphy's Law) dictates that it will do so just as I'm attempting something that requires great delicacy and precision.

If we ignore wind resistance and assume the poster falls with the same orientation as above (instead of, say, turning over a few times), we can calculate the time it takes to hit the ground and the velocity it has when it does so.

Lesse... acceleration due to gravity= -9.8 m/s/s

initial velocity= 0m/s 

displacement= -1.168 m

and displacement=initial velocity*time=.5*acceleration*time*time

Plug in the information we have (paying special attention to our signs), solve for time, bake until golden brown and let stand for twenty minutes...

time= .488 seconds. (No wonder it always takes me by surprise.)

Next we can find velocity right before it hits the floor, because

instantaneous velocity=initial velocity+acceleration*time

la la la

Final velocity= -4.782 m/s

So now, when my poster falls just as I'm putting the final touches on my toothpick Eiffel Tower, at least I can console myself with knowing both the time it was falling and the velocity it had before impact. Then I can go find a really big hammer.