Discussion 5: Newton's law
We had to do a discussion on: in one of my demonstrations, I let someone break concrete blocks that are placed on top of me while I am sandwiched between two beds of nails.Using your knowledge on Newton’s laws, explain how the nails do not penetrate into my body. So, attached are 2 essays written about this. Please tell what you liked about each one, if you would add anything to it, or if questions need to be asked, ask them as well. Please write one page per discussion and keep them separate.
To begin, a bit of background information on the nail bed not directly related to one of Newton’s laws is pressure. Pressure is defined as force/area. The nail bed in the picture had a multitude of nails spread out. As a result, the pressure at a single tip of a nail is not enough to puncture the skin since there is a large surface area for the pressure to be distributed about. In relation to Newton’s first law we know that all objects possess inertia, which is a resistance in change of motion. His first law states that, “objects at rest tend to remain at rest and objects in motion tend to remain in motion.” In this particular instance, the large black is a big mass, which means it wont move much due to its inertia. This minimalizes the chances of being stabbed by the top nail bed since the lack of inertia of the block prevent the nail bed from moving much during impact. In addition, Newton’s third law makes us consider that you can get an equal reaction from the area of which force is acted upon. If the person in the picture were asked to rest on one, two, or three nails, the reaction would be very high. If the person illustrated in the picture had a force of 650 newtons that is the amount that would be reacted upon the few needles. So the more needles on the nail bed the safer the experiment becomes.
Ever since I was little, magicians who did this "bed of nails" trick would always amaze me. I always wondered how in the world this was possible. I finally got my answer in grade 8, when we discussed Newton's Laws.
Newton's first law clearly states that all massive objects possess inertia, which is a resistance to change in motion. "An object at rest tends to stay at rest, while an object in motion tends to stay in motion" - is the most commonly used phrase to describe this law. The concrete block clearly is very massive, and possesses inertia. The inertia of the block will not allow the upper bed of nails to move much during the impact between the hammer and block. The chances of the Professor being stabbed are minimized greatly.
Pressure also has a great impact on the outcome of this "trick". Pressure is defines as force/area. There is a large number of nails on the bed, which we could classify as the large area. Also, the professors surface area large enough to be in contact with many nails, resulting in the nails not being forceful enough to penetrate skin.
The kinetic energy of the sledgehammer is lagged through the bricks, making it impossible for the energy to be strong enough to transfer into the bed of nails - stabbing the professor.
Discussion 5
Name
Institutional Affiliation
Discussion 5
Discussion 1:
There is an element of the law of inertia omitted from the explanation. Newton’s law of inertia proposes that all objects remain in their state of rest or uniform motion unless they are acted upon by an external force. Due to the size of the hammer and the downward movement, there is an external force sufficient to move the concrete block and thus propel the nails to penetrate the skin. In addition, the concept of large motions is not true because according to the laws of motion, there is a relationship between mass, force and acceleration. Therefore, regardless of the size of an object, it is always possible to make it move.
I completely agree with the concept of the many nails, reducing pressures to a degree where the force on any single nail is insufficient to penetrate the skin. Pressure is inversely proportional to surface area. This is to say the bigger the area, the less the pressure. For example, even without the sledgehammer, lying on a nail is dangerous because the pressure applies on the tip of the single nail is sufficient to penetrate the sin. However, having many nails distributes the pressure exerted by the body weight and thus minimizes the risk of penetration. The same concept applies to the sledgehammer.
In addition, it is important to consider the concept of energy conversion. The sledgehammer generates a big momentum as it comes down. This momentum may be considered as kinetic energy. Upon impact with the concrete block, the energy is used to disintegrate the block, thus converting the kinetic energy into other forms. This conversio...