Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://zebu.uoregon.edu/1998/ph101/l15.html
Дата изменения: Fri Nov 20 00:29:47 1998 Дата индексирования: Tue Oct 2 01:04:24 2012 Кодировка: |
We have been probing Newton's through our studies of Momentum and Energy Conservation.
Below is a brief summary of Newton's three laws along with momentum and energy conservation. This should be familiar to you.
Kinetic and Potential Energy:
Throwing a ball into the air represents a situation in which the total energy is fixed and there is a continous transformation from kinetic energy to potential energy.
Kinetic Energy = Energy Associated with Motion
1/2 mass * Velocity * Velocity = 1/2mv2
Momentum is Mass * Velocity = mv
Conservation of Momentum is a rule of mechanics. your intution has already told you about it.
Consider hitting a baseball. The bat, with some mv, makes impulsive contact with a ball - mbat is greater than mball and since:
then vball is greater than vbat (provided that you hit the ball and not just air).
Same principle holds in the situation of cannon recoil:
Potential Energy --> object has a position in a force field
Potential Energy = mass * grav. acceleration * height
PE = mgh
g = gravitational acceleration of the earth
since F = ma and since the earth exerts a continuous gravitational force on all objects of mass, m, then the manifest force is
F = mg this is what weight is !
Now look what Newton says we can now do:
Applications of Conservation of Momentum: