# Inelastic collision, determine ratio KEf/KEi

• Anonymous123451234
In summary, the question asks for the approximate ratio of final kinetic energy to initial kinetic energy in two extreme cases of completely inelastic collisions. These cases involve a moving train colliding with a stationary car and a moving car colliding with a stationary train. Despite not being given specific values for masses or velocities, the answer can be approximated using typical values and the ratios will not depend on the specific choices. The question also asks for the final velocity in each case, the final mass of the two bodies in case (a), and the acceptable range for the ratio of final to initial kinetic energy values. To solve this problem, unknowns can be used for the masses and collision speed, and the effects of the mass ratio can be considered in
Anonymous123451234
Consider the following extreme cases for a completely inelastic collision. In each case, determine the approximate ratio KEf/KEi.
a) A moving train collides with a stationary car.
b) A moving car collides with a stationary train.

I do not understand this question, I'm not given masses or velocities. Can anyone explain?

You can use typical values, the answer won't depend on your specific choice. You are asked for approximations. A car might have a mass of 500 kg (very light car) or 3000 kg (very heavy car), but it won't have a mass of 10 kg or 100,000 kg.

Hello,

I suppose KEf/KEi is the ratio Final Kinetic Energy / Initial Kinetic Energy.

You must answer the following questions:

1) What will be the final velocity (approximately) in each case?
2) What will be the final mass of the two bodies in case (a)?
3) What is the ratio Final Kinetic Energy / Initial Kinetic Energy (simplify the fraction till you get a number)?
4) What is the acceptable range for KEf/KEi value?

Anonymous123451234 said:
Consider the following extreme cases for a completely inelastic collision. In each case, determine the approximate ratio KEf/KEi.
a) A moving train collides with a stationary car.
b) A moving car collides with a stationary train.

I do not understand this question, I'm not given masses or velocities. Can anyone explain?
Rather than plug in numbers (pace @mfb), I would create unknowns: m for the mass of the car, M for the much larger mass of the train, and u for collision speed. Once you have the formulae for the energy ratios, you can consider how they are affected by the mass ratio.

## 1. What is an inelastic collision?

An inelastic collision is a type of collision where kinetic energy is not conserved. This means that some of the kinetic energy of the system is lost during the collision, usually due to the objects deforming or sticking together.

## 2. How is the ratio of KEf/KEi determined in an inelastic collision?

The ratio of final kinetic energy (KEf) to initial kinetic energy (KEi) can be determined by dividing the final kinetic energy by the initial kinetic energy. This ratio can also be expressed as a percentage to show the amount of kinetic energy lost during the collision.

## 3. What factors affect the ratio of KEf/KEi in an inelastic collision?

The ratio of KEf/KEi can be affected by the type of objects involved in the collision, their masses, and the speed at which they are moving. The angle of collision and the presence of external forces can also impact this ratio.

## 4. How does the ratio of KEf/KEi differ in an inelastic collision compared to an elastic collision?

In an elastic collision, the ratio of KEf/KEi is equal to 1, meaning that kinetic energy is conserved. In an inelastic collision, the ratio is less than 1, indicating that some kinetic energy has been lost during the collision.

## 5. What are some real-world examples of inelastic collisions?

Some examples of inelastic collisions include a car hitting a wall, a golf club hitting a golf ball, and a person catching a ball with their hand. In each of these scenarios, some kinetic energy is lost due to the objects deforming or sticking together upon impact.

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