Is this an elastic or inelastic collision?

In summary, the conversation is about preparing for an Elastic Collision lab and checking prelab questions. During the discussion, a calculation is done to find the final speed of a 5 kg object after colliding with a 10 kg object moving towards it. It is determined that the collision is inelastic, despite being for an elastic collision lab, due to the calculation of kinetic energies. The final speed is found to be -2 m/s.
  • #1
new324
30
0
Im preparing for an Elastic Collision lab today and was wondering is someone would check my prelab questions.

A 5 kg object traveling at 4 m/s collides head on with a 10 kg object moving toward it with a speed of 3 m/s. The 10 kg object stops dead after the collision.

a) What is the final speed of the 5 kg object?

I used conservation of momentum.

p1i + p2i = p1f + p2f

20 - 30= p1f + 0; p1f= -10; v1f= -2 m/s

b) Is the collision elastic? This is where i question myself. Since the lab is for an elastic collision I would think it would be elastic. However, when I plug these values into their KE values it seems otherwise.

KE1i + KE2i = KE1f + KE2f

(.5 * 5 * 16) - (.5 * 10 *9) = (.5 * 5 * 4) + 0
Since 40 - 45 = 5; and KE1f = 10; It is inelastic. Right?
 
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  • #2
10 is your final speed not Ke for inelastic collisions use only conservation of momentum
 
  • #3
new324 said:
b) Is the collision elastic? This is where i question myself. Since the lab is for an elastic collision I would think it would be elastic. However, when I plug these values into their KE values it seems otherwise.

KE1i + KE2i = KE1f + KE2f

(.5 * 5 * 16) - (.5 * 10 *9) = (.5 * 5 * 4) + 0
Since 40 - 45 = 5; and KE1f = 10; It is inelastic. Right?
It is inelastic, but there is no negative sign when you calculate the kinetic energies. Therefore the initial kinetic energy of the system is 85 J.
 

1. What is an elastic collision?

An elastic collision is a type of collision in which there is no loss of kinetic energy. This means that the total kinetic energy before the collision is equal to the total kinetic energy after the collision.

2. What is the purpose of an elastic collision lab?

The purpose of an elastic collision lab is to demonstrate the principles of conservation of momentum and conservation of kinetic energy. It allows for the study of the behavior of objects before, during, and after a collision and helps to understand the concept of elastic collisions.

3. What materials are needed for an elastic collision lab?

To perform an elastic collision lab, you will need two objects of different masses, a flat surface, a ruler or meter stick, a stopwatch, and a level surface to perform the experiment on. You may also need a video camera or smartphone to record the collisions for further analysis.

4. How do you calculate the velocities of the objects in an elastic collision?

To calculate the velocities of the objects in an elastic collision, you will need to use the equations of conservation of momentum and conservation of kinetic energy. These equations take into account the masses and velocities of the objects before and after the collision, as well as the angle of collision.

5. What are some real-life examples of elastic collisions?

Elastic collisions can be observed in many real-life situations, such as when two billiard balls collide on a pool table, when two cars collide and bounce off each other, or when a tennis player hits a ball with their racket. In all of these examples, the objects involved bounce off each other without any loss of kinetic energy.

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