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### Topic: Little physics brain teaser (Read 1 time)previous topic - next topic

#### N_Tesla

##### Aug 30, 2013, 07:04 pm
This video has been around for about a week (even SA talked about it). Two identical wooden blocks are shot from below. One on the center, the other one off-center. Which one goes the highest and why ?

Watch the previous video and take a guess.
Result
Explanation

Did you guessed correclty? I did :-)

#### wizdum

#1
Blasphemy.

#2
##### Aug 31, 2013, 12:02 am
Why is the question?
Is anybody measuring the mass, energy and direction of the bodies ?
If not what is the question and does it have any meaning?

#### RPCoyle

#3
##### Aug 31, 2013, 02:18 am
It doesn't seem to follow Ohm's law.

#### John_Smith

#4
##### Aug 31, 2013, 08:59 am
They write off explanations due to wind resistance as too small to consider, yet the x-ray showing the same depth of bullet depth is fobbed off.

As several people have asked, I would like to see this with a much longer beam, with the gun aimed at the very end.

I know from sailing that you lose a lot of speed if the sail is flapping around and spilling wind, it could be that the block fired from its centre builds up a cushion of air above it that slows its ascent ?

It would be interesting to see a baby version in a vacuum .  Perhaps a nice experiment for NASA ( or China ) to do on the next moon trip :-)   :*

45 years of editing projects with a knife and soldering iron, then I found Arduino !

#### dc42

#5
##### Sep 01, 2013, 03:23 pm
This is a variation on the classic "sticky collision" problem. Linear momentum is conserved. The linear momentum of the bullet is transformed into linear momentum of the bullet+wood. So the initial vertical speed of the centre of mass of the block is the same in both cases. In a sticky collision, the kinetic energy of the final (combined) body is always less than the total initial kinetic energy of the two bodies, and the excess energy is normally dissipated as heat in the collision. In the case of the block hit off-centre, some of this excess energy goes into rotational kinetic energy instead.
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