58 The Poetry of Physics and The Physics of Poetry
that of the recoiling gun is due to the large difference in their masses.
The momentum of the gun’s recoil and the bullet are equal and opposite,
however. Momentum is the product of the mass times the velocity of a
body. Momentum therefore has both direction and magnitude just like
the velocity. In the example of the bullet and the gun the magnitude of
the momentums are equal, their directions are opposite however and
therefore when they are added they cancel. Both the example of the diver
and the raft and the discharge gun illustrate the principle of the
conservation of motion.
The magnitude of the momentum is a measure of how much inertia or
motion a body is carrying. A very light object like a bullet is still very
dangerous because if it is moving fast enough it carries a great deal of
momentum. Of course if it travels at only one kilometer per hour there is
no problem. A slowly moving object on the other hand, which is very
heavy can also be dangerous. One does not wish to be caught between
two freight cars even if they are only traveling at one kilometer per hour.
The momentum is a measure of the amount of force a body can exert on
others through collisions or as one of my students so aptly expressed it:
“momentum is crushing power.”
The transfer of momentum from one body to another is equivalent to
the action of a force. In fact a force may be defined as an action of one
body on another, which changes its momentum. Because the forces
between two bodies are equal and opposite the total amount of
momentum in any given interaction of two bodies is conserved. This is
most easily observed by observing the elastic collisions of metal balls in
the adjoining Fig. 6.3.
Fig. 6.356 The Poetry of Physics and The Physics of Poetry
the magnitude of the momentums are equal, their directions are opposite
however and therefore when they are added they cancel. Both the
example of the diver and the raft and the discharge gun illustrate the
principle of the conservation of motion.
The magnitude of the momentum is a measure of how much inertia or
motion a body is carrying. A very light object like a bullet is still very
dangerous because if it is moving fast enough it carries a great deal of
momentum. Of course if it travels at only one kilometer per hour there is
no problem. A slowly moving object on the other hand, which is very
heavy can also be dangerous. One does not wish to be caught between
two freight cars even if they are only traveling at one kilometer per hour.
The momentum is a measure of the amount of force a body can exert on
others through collisions or as one of my students so aptly expressed it:
“momentum is crushing power.”
The transfer of momentum from one body to another is equivalent to
the action of a force. In fact a force may be defined as an action of one
body on another, which changes its momentum. Because the forces
between two bodies are equal and opposite the total amount of
momentum in any given interaction of two bodies is conserved. This is
most easily observed by observing the elastic collisions of metal balls in
the adjoining Fig. 6.3.
Fig. 6.3If one ball falls on the others at rest momentum is transferred from
ball 1 to 2 to 3 to 4 to 5, with the result that ball number 5 goes flying off
with the same momentum as ball number 1. In second case the
momentum is double because we let two balls fall, which transfers