Collision & Momentum: Observing Elasticity, Momentums & Velocities

In summary, the conversation was about an experiment where two magnetic air pucks were collided on an air table and the goal was to determine the momentums and velocities and prove that it was an elastic collision. The total momentum before the collision was found to be 0.493 m/s*kg and after the collision it was 0.520 m/s*kg, resulting in a 5.2% error. The conversation also discussed possible reasons for this error, such as human error in calculations and measuring, as well as the impact of friction on the results. It was also mentioned that the experiment was done on an air table to reduce friction. The conversation concluded with a discussion about the effect of a slanted air table on the collision
  • #1
applesnjanono
7
0
The assignment was to observe the collision between two magnetic air pucks and determine the momentums and velocities at various points. This type of collision was elastic, and i had to prove this. So since this collision should be elastic, the total momentum before should equal the total momentum after the collision.

I ended up with the total momentum before the collision to be 0.493 m/s*kg and the total momentum after the collision to be 0.520 m/s*kg. This answer resulted in a 5.2% error. Following these calculations, I had to disscuss why this percent error occurred. Any ideas?
 
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  • #2
Elastic means that energy is conserved. You did the wrong calculation.
 
  • #3
This was an actual experiment. Two air pucks were placed on an air table. Airpuck one starts moving and airpuck two is stationary. Soon airpuck one collides with airpuck two. Dots were made on a piece of paper to observe the acutal movement and track of the two pucks. And from this we had to calculate momentum and velocity. So since this was an acutal experiement, chances of getting exactly an elastic collision is rare. There is a high chance of error in the experiment. And this is what i got. A percent error of 5.2%. But i don't know how to explain why.. besides human error of calculating and measuring.
 
  • #4
an elastic collision would imply kinetic energy is constant as DavidWhitbeck said.

So, then all the energy in the system should be entirely kinetic. Meaning that the only type of energy in the system is kinetic energy.

Why do you think the experiment was done on an air table instead of just sliding the puck on a regular table?
 
  • #5
I think it was done on an air table rather than a regular table because this would cause less friction to occur. If there was more friction, then more kinetic energy and momentum is lost.
 
  • #6
applesnjanono said:
I think it was done on an air table rather than a regular table because this would cause less friction to occur. If there was more friction, then more kinetic energy and momentum is lost.

Even though there is less friction, there still is friction and so energy was lost as heat due to friction. Which might have used up enough energy such that the kinetic energy before was not the energy after and that could be why you got such a high error
 
  • #7
applesnjanono said:
This was an actual experiment.

This type of collision was elastic, and i had to prove this.

Okay then

(a) you do not "prove" as you put it anything in an experiment. There is no such thing as proof in scientific experiments.

(b) you can not simply assume that the collision is elastic, but you can test it.

I'm just saying that if you are trying to test to see if the collision was elastic, then you do not compute the total initial and final momentum, you instead compute the initial and final total kinetic energy.
 
  • #8
what if the air table was slanted? how would this affect the collision of the two air pucks?
 
  • #9
applesnjanono said:
what if the air table was slanted? how would this affect the collision of the two air pucks?

Since the collision took place on a plane, it doesn't matter if the table was slanted or not, as in, elastic collision would remain elastic.

However, in our case it matters because, in case of a slanted table, an external force acts on both the airpucks [i.e. a net external force acts on the system] and hence conservation of momentum does not follow. Even though in the case of a slanted table, the frictional force acting is less, for considerably big angles [as in.. 6-7 degrees and greater], the gravitational force assisting motion would be considerably more than the frictional force [because the [itex]\mu[/itex] of the air table is very small].
 
  • #10
You can prove, what for normal puck, which is spinning, friction is
[tex]F=\mu{mg\frac{v}{\omega{R}}}[/tex]
where R - radius, v - linear velocity, [tex]\omega[/tex] - angular velocity...
 
  • #11
would air resistance being neglected affect the results in anway?
 

What is the definition of collision?

Collision is an event in which two or more objects come into contact with each other, resulting in a change in their velocities.

What is momentum?

Momentum is a measure of an object's motion, determined by its mass and velocity. It is a vector quantity, meaning it has both magnitude and direction.

What is elasticity?

Elasticity is the ability of an object to return to its original shape after being deformed by an external force. In the context of collisions, it refers to the degree to which objects bounce off each other after impact.

How is momentum conserved in a collision?

In a closed system, the total momentum before a collision is equal to the total momentum after the collision. This is known as the law of conservation of momentum.

What factors affect the elasticity of a collision?

The elasticity of a collision is affected by the materials and surfaces of the objects involved, as well as the amount of force applied during the collision. Objects with more elastic materials and surfaces will bounce off each other with less energy loss compared to objects with less elastic materials and surfaces.

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