Jump to content
  • entries
    30
  • comments
    35
  • views
    4,603

Firing a Gun


jwdiehl88

1,093 views

Recently I was watching Point of Interest, a TV show, and I was thinking about what kind of physics are behind firing a gun.  I concluded that when the shooter shoots a gun, the force on the bullet is equal to that on the gun-shooter. This is due to Newton's third law of motion (for every action, there is an equal and opposite reaction).  The force of the bullet is equal to the gun-shooter due to the law of conservation of momentum.  A person with a gun have a combined mass M and the bullet has a mass m. When the gun is fired, the two systems move away from one another with new velocities V and v respectively.  Also, the person with a gun moves in the opposite direction of the bullet.  Therefore, the initial momentum is equal to the final momentum due to the law of conservation of momentum.  Since the net force is equal to the change of momentum, the initial change of momentum of the person and gun is equal to the final bullet's momentum.  Therefore, the person with a gun has a equal force and a opposite direction of the bullet.  

3 Comments


Recommended Comments

As a person who does a good amount of shooting, it is really cool to see this relationship play out.  Especially when you shoot guns of the same power, but with different masses, it is easy to see how the lack of mass of the gun is made up for by the increased velocity the gun hits your shoulder with.

Link to comment

Absolutely.  I can remember going to a class where we were on the range and a little old lady was learning to shoot and thought she'd be fine because she had a small little "pocket revolver," and was surprised how tough it was to control.  Giving her a much larger semi-automatic, she found hitting the target was a piece of cake.  Larger mass, smaller acceleration, easier to control!

Link to comment
Guest
Add a comment...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...