My teacher asked me: "Why don't you break your hand when you break the
three cinder blocks?" The answer has to do with Newton's Second Law of Motion
This law of motion states that the acceleration of an object is directly proportional to
the net force acting on the object. Another way to say this is that force (F) is equal to
the mass (m) of the object times the acceleration (a) of the object.
My hand has mass and the more that I can increase the speed of my hand moving downward
means that I will be increasing the amount of force to the blocks. The blocks are at rest; they are
not moving. If I moved my hand too slowly I could not break the blocks. You can see this motion in a video that I
have to be downloaded.
Click here for the block breaking video (no sound).
If you watch the video you will see that I move my hand slowly at first to take aim, but I move it quickly when I really decide to break the cinder blocks.
Think of what would happen if the three cinder blocks were dropped on my hand.
Now the blocks would be moving, and my hand would be at rest. The blocks would
accelerate due to gravity. The blocks have mass and with their acceleration they would
put a lot of force on my hand, maybe breaking it (then I would have to go to the hospital).
I also break pine boards. They are easier to break than the cinder blocks because they have less
mass. Since they have less mass, they need less force to break meaning that I can move my
hand more slowly (less acceleration). Another video of me breaking pine boards is also available.
Click here to get the board breaking video (also without sound).
I have had formal training in breaking. You should not try to break boards or blocks without proper training. I have to have positive confidence to break boards and blocks and this takes a lot of practice and training.