# 1D Elastic Collision between an Elephant and a Fly

• ObitoLegend
In summary, the conversation discusses finding the final velocity of a fly based on the initial velocity of an elephant. The equation used is v'2=(2m1/(m1+m2))*2.1m/s, where m1 and m2 represent the masses of the elephant and the fly, respectively. It is mentioned that m1>m2 and that this information does not help in solving the equation. The conversation then moves on to discussing the sum and difference of 1 million plus or minus one, and it is concluded that the difference between the two values is positive. Finally, it is mentioned that the small mass of the fly is negligible compared to the mass of the elephant.
ObitoLegend
Homework Statement
A hovering fly is approached by an enraged elephant charging at 2.1 m/s. Assuming that the collision is elastic at what speed does the fly rebound? Note that the projectile(the elephant) is much more massive than the stationary target (the fly)
Relevant Equations
1-D Elastic collisions where v2 = 0:
v'1 = ((m1-m2)/m1+m2)*v1
v'2 = (2m1/(m1+m2))*v1
1 = elephant
2 = fly
So I am trying to find v'2 which is the final velocity of the fly. I have v1 the initial velocity of the elephant 2.1m/s. So I plug it into the equation and have v'2=(2m1/(m1+m2))*2.1m/s. We are not given the masses so I just know m1>m2 but I don't understand how that will help me, or how we can get rid of the masses to solve the equation.

If m1>>m2, what does that say about their sum and difference?

That they are both positive?

ObitoLegend said:
That they are both positive?
What is 1 million plus or minus one? How does it compare to 1 million?

ohh so I can disregard m2 because m2 is so small compared to m1

ObitoLegend said:
ohh so I can disregard m2 because m2 is so small compared to m1
Yes. The elephant is a moving wall essentially.

got it thank you!

Frabjous

## 1. What is a 1D elastic collision between an elephant and a fly?

A 1D elastic collision is a type of collision in which both the momentum and kinetic energy of the objects are conserved. In this scenario, an elephant and a fly collide in a straight line and both objects bounce off each other without any loss of energy.

## 2. Can an elephant and a fly really collide in a 1D elastic collision?

In theory, yes, it is possible for an elephant and a fly to collide in a 1D elastic collision. However, in reality, the size and mass difference between the two objects would make it highly unlikely for such a collision to occur.

## 3. How does the mass of the objects affect the outcome of the collision?

The mass of the objects plays a significant role in the outcome of the collision. In a 1D elastic collision, the lighter object (in this case, the fly) will experience a greater change in velocity compared to the heavier object (the elephant).

## 4. What happens to the momentum and kinetic energy of the objects after the collision?

In a 1D elastic collision, both the momentum and kinetic energy of the objects are conserved. This means that the total momentum and kinetic energy before the collision is equal to the total momentum and kinetic energy after the collision.

## 5. Are there any real-life applications of a 1D elastic collision between an elephant and a fly?

While this scenario may seem far-fetched, the concept of 1D elastic collisions is commonly used in physics and engineering to understand the behavior of objects in motion. It can also be applied to real-life scenarios, such as in sports where balls collide with each other or in car crashes where the vehicles bounce off each other without significant damage.

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