Conservation of momentum Definition and 757 Threads

In Newtonian mechanics, linear momentum, translational momentum, or simply momentum (pl. momenta) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If m is an object's mass and v is its velocity (also a vector quantity), then the object's momentum is





p

=
m

v

.


{\displaystyle \mathbf {p} =m\mathbf {v} .}
In SI units, momentum is measured in kilogram meters per second (kg⋅m/s).
Newton's second law of motion states that the rate of change of a body's momentum is equal to the net force acting on it. Momentum depends on the frame of reference, but in any inertial frame it is a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum does not change. Momentum is also conserved in special relativity (with a modified formula) and, in a modified form, in electrodynamics, quantum mechanics, quantum field theory, and general relativity. It is an expression of one of the fundamental symmetries of space and time: translational symmetry.
Advanced formulations of classical mechanics, Lagrangian and Hamiltonian mechanics, allow one to choose coordinate systems that incorporate symmetries and constraints. In these systems the conserved quantity is generalized momentum, and in general this is different from the kinetic momentum defined above. The concept of generalized momentum is carried over into quantum mechanics, where it becomes an operator on a wave function. The momentum and position operators are related by the Heisenberg uncertainty principle.
In continuous systems such as electromagnetic fields, fluid dynamics and deformable bodies, a momentum density can be defined, and a continuum version of the conservation of momentum leads to equations such as the Navier–Stokes equations for fluids or the Cauchy momentum equation for deformable solids or fluids.

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  1. colemc20

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    My only issue is what this would look like. I can't draw a respective picture.
  2. S

    Determining position of an object after inelastic collision

    Homework Statement A 39,000 lb truck A and a 3968 lb sports car B collide at an intersection. At the moment of the collision, the truck and the sports car are traveling with speeds vA = 70 mph and vB = 30 mph. Assume that the entire intersection forms a horizontal surface. Letting the line of...
  3. F

    Ballistocardiograph and conservation of momentum

    Hi, once again I'm probably asking a question that is more about human physiology than physics (I recently asked a question that had to do with hearing). I found a (definitely too hasty) reference to a ballistocardiograph in a high school textbook. So I got curious about the way this apparatus...
  4. J

    Railway/Cannon - Conservation of Momentum HW Problem

    Hello forum. I have a HW question that I don't fully grasp just yet. It was multiple choice and somehow I guessed the right answer based on the work I did complete, but I want to know how to get to the solution and which steps I'm leaving out. I'll follow the format to write out the...
  5. P

    Ice Skating conservation of momentum (conceptual problem)

    Homework Statement Two ice skaters have masses m1 and m2 and are initially stationary. Their skates are identical. They push against one another, as in Figure 7.11, and move in opposite directions with different speeds. While they are pushing against each other, any kinetic frictional forces...
  6. Np14

    Rocket: conservation of momentum

    Homework Statement A fireworks rocket is moving at a speed of 45.0 m/s. The rocket suddenly breaks into two pieces of equal mass, which fly off with velocities v1 and v2. What are the magnitudes of v1 and v2? Homework Equations Conservation of Momentum m1v1 + m2v2 = m1vo1 + m2vo2 The...
  7. P

    Conservation of momentum - trampoline

    English isn't my main language, so I apologize in advance if something is unclear. We are leaving air resistance out of this problem! 1. Homework Statement We are going to describe the force F from the trampoline on the Joe as F = kx, k is a spring constant. This is a model. 1. Joe drops...
  8. S

    Percent error in conservation of momentum lab confusion

    Okay, so I did an elastic collision with Vernier carts and magnets. The results seem pretty good. Cart one started with -0.1205 kg*m/s ended with +0.1027 kg*m/s Cart two started with +0.1174 kg*m/s ended with -0.1118 kg*m/s So Total before = -0.0031 kg m/s and total after = -0.0091 kg m/s. If...
  9. Mason Smith

    Question involving the conservation of momentum

    Homework Statement Homework Equations The conservation of momentum states that if there are no external forces acting on a system, then momentum is conserved (i.e., the momentum before an event is equal to the momentum after an event). (Note: We assume that the internal forces follow Newton's...
  10. B

    A Measurement and the Conservation of Momentum

    If you prepare a particle with a “relatively precise” momentum by the act of filtering or measuring its momentum. It’s state will collapse into a momentum eigenstate and the measured momentum will be the corresponding eigenvalue. The position state will now be nearly uniformly spread out and...
  11. J

    Conservation of Momentum (Explosion Kinematics)

    Homework Statement [/B] A 3200 kg space vehicle (including a launchable lifeboat) is traveling with a velocity of 300 m/s in a straight trajectory [East]. The lifeboat (200 kg) is fired at a speed of 1000 m/s [N of original trajectory]. a) After firing it is found that the horizontal...
  12. E

    Conservation of momentum and angular momentum

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  13. A

    Conservation of Momentum Space Ship Problem

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  14. K

    Conservation of momentum in two dimensions

    Homework Statement A bomb initially at rest is exploded into three pieces on a smooth, horizontal surface. Two pieces fly off at a 60° angle to each other, a 2.0 kg piece at 20 m/s and a 3.0 kg piece at 12 m/s. The third piece flies off at 30 m/s with an unknown direction. Determine the...
  15. P

    Final velocities of two objects in a 2D elastic collision

    Homework Statement An atomic nucleous of mass m traveling with speed v collides elastically with a target particle of mass 3.0m (initially at rest) and is scattered at 45o (a). What are the final speeds of the two particles? Advice: eliminate the target particle's recoil angle by manipulating...
  16. Akash47

    How Does the Velocity of a Raft Change When Four Men Jump Off Simultaneously?

    Suppose four men are on a square shaped raft.All have jumped mutually perpendicularly into the river from the raft at velocity 2m/s at the same time. What will be the velocity of the center of mass of the raft? The implied assumption is likely that the mass of the four men is same. I think the...
  17. L

    Simple Ice Skater with Conservation of Angular Momentum

    Homework Statement Not a HW problem, but a "me re-thinking things" problem. Please tell me where my thinking is flawed: You have an ice skater with no net external torques acting on him/her. (We are analyzing the time after they have to get an external torque on them by pushing off of the...
  18. Akash47

    What Will Be the Velocity of the Center of Mass of the Raft?

    Homework Statement Suppose your three friends and you are on a square shaped raft. You all have jumped mutually perpendicularly into the river from the raft at velocity 2m/s at the same time. What will be the velocity of the center of mass of the raft? Homework Equations Maybe,the law of...
  19. Krushnaraj Pandya

    Conditions for conservation of momentum

    Homework Statement Consider a classic wedge and block system, (block on top of wedge(inclination theta)). there is friction between the block and wedge (not enough to prevent block from sliding). All other surfaces are smooth. For the motion that follows after releasing the block from rest, is...
  20. R

    Physics 30 question about conservation of momentum

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  21. C

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    I'm a passout from school taking a gap year. I find the concept of conservation of momentum exceedingly difficult. Each question - and sometimes each part of a question, if a question has different parts - requires us to choose different systems each time. I look at the solution, and think I...
  22. jxj

    Isolating Variable in Equation for conservation of momentum

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  23. jfizzix

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  24. G

    Maximizing rocket velocity - shoot fuel at once, or slowly?

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  25. M

    Conservation of momentum - with understanding

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  26. S

    Conservation of momentum & energy

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  27. J

    D’Alambert vs Newton’s second law?

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  28. E

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  29. D

    Combining conservation of momentum and kinetic energy

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  30. valovato

    Momentum transfer from linear to angular motion

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  31. Kate2018

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  32. A

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  33. A

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  34. T

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  35. F

    Conservation of Momentum With Changing Mass

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  36. K

    Conservation of Momentum Lab (Carts Collide and Stick Together)

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  37. O

    I Photonuclear reaction & Conservation of momentum

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  38. U

    Conservation of linear momentum in this system

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  39. Lukanol

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  40. S

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  41. C

    Other Physics EE (Extended Essay) Advice: Conservation of momentum

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  42. S

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  43. B

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  44. J

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  45. I

    Two-ended rocket - Conservation of Momentum

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  46. S

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  47. Amaterasu21

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  48. Richardparker800

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  49. Pbaseball

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