How can conservation of momentum explain the behavior of Newton's cradle?

In summary, the conversation discusses the behavior of Newton's cradle, which involves the conservation of momentum and mechanical energy. However, in order to fully explain the observed behavior, an additional condition, such as a shock wave propagating dispersion-free through the chain, must also be considered. This allows for the prediction that the number of balls that move on the left will equal the number of balls that emerge on the right.
  • #1
rebellion
1
0

Homework Statement


so, i have a problem. see the pic
http://img255.imageshack.us/img255/4628/aughhm9.png
the question is. if we have, for example 10 balls standin like that, if we move the ball which is on the right, only one will move, the left one. if we move two of them from the right, two of them will move on the left also.

Homework Equations



Ft = mv to satisfy the conservation of momentum

The Attempt at a Solution



the solution is that something else is satisfied, i know that the momentum is satisfied but something is missing. please help :-)

thanks in forward
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
Mechanical energy is also conserved.
 
  • #3
I don't get your question. What exactly are you asking?
 
  • #4
From Wikipedia
http://en.wikipedia.org/wiki/Newton's_cradle

The behaviour of the pendulum follows from the conservation of momentum and energy only in the case of two pendula. Indeed, if there are r pendula there are also r unknown velocities to be calculated from the initial conditions. An additional condition for the observed outcome is that a shock wave has to propagate dispersionfree through the chain.
 
  • #5
It is certainly true that it takes more than simple conservation of momentum and energy to derive the observed behavior of Newton's cradle. Most textbooks pull a fast one and just assume that however many balls move after the collision, they all move together. (And no rebounding.)

Using this you can show that the number of balls swung on the left will equal the number of balls that will emerge on the right.
 

FAQ: How can conservation of momentum explain the behavior of Newton's cradle?

What is conservation of momentum?

Conservation of momentum is a fundamental principle in physics that states that the total momentum of a closed system remains constant over time. This means that the combined momentum of all objects in the system before and after a collision or interaction must be equal.

How is momentum conserved in a closed system?

In a closed system, momentum is conserved through the principle of action and reaction. This means that any force applied to one object will result in an equal and opposite force on another object, causing their momenta to cancel out and remain constant.

What is the equation for calculating momentum?

The equation for momentum is p = mv, where p is momentum, m is mass, and v is velocity. Momentum is measured in units of kilogram-meters per second (kg*m/s).

How does conservation of momentum apply to everyday situations?

Conservation of momentum applies to many everyday situations, such as car collisions, ball bouncing, and even walking. When a car collides with another car or object, the total momentum of the system before and after the collision must be equal. This can help explain the direction and speed of the objects after the collision. Similarly, when you walk, your legs push against the ground, causing the ground to push back with an equal and opposite force, allowing you to move forward.

Are there any exceptions to the conservation of momentum?

Conservation of momentum is a fundamental law of physics, and as such, it applies to all closed systems. However, in situations involving extremely high speeds or microscopic particles, the principles of quantum mechanics may come into play, causing some deviations from classical conservation of momentum. However, these exceptions are only observed in very specific and extreme situations and do not apply to most everyday scenarios.

Similar threads

Conservation of momentum when a ball hits a wall
Replies
9
Views
4K
Newtons cradle, conservation of momentum
Replies
4
Views
2K
Question involving the conservation of momentum
Replies
4
Views
2K
How Does Angular Momentum Conservation Affect Asteroid Collision Dynamics?
10
Replies
335
Views
11K
Solving Elastic Collision of Two Balls: Theory & Solutions
Replies
15
Views
2K
Momentum in different referance frames
Replies
6
Views
1K
Angular momentum conservation in collision with a nail
Replies
9
Views
1K
Conservation of momentum - trampoline
Replies
5
Views
2K
Why is momentum conservation always true in a collision?
Replies
4
Views
1K
Conservation of Momentum and Energy
Replies
8
Views
2K

Hot Threads

Recent Insights

Back
Top