Inelastic Collision Question

In summary, the conversation discusses a physics problem involving a box hanging from the ceiling and a bullet hitting it. The question asks for the speed of the bullet, and the solution involves using conservation of energy and momentum to determine the velocity of the bullet and the box-bullet combo. It also assumes an instant collision between the two objects.
  • #1
wessleym
2
0
Here's a question for anyone out there who would really like to less than moderately challenge their physics skills:
There is a 40 kilogram box hanging from the ceiling, at rest. A bullet with a mass of 0.01 kilogram hits it, forcing it to swing back on the ropes. As it swings back, it gets 0.02 meters off of the ground. Assume the box's bottom remains parellel with the ground. How fast was the bullet moving? Thanks to anyone who can figure this one out!
 
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  • #2
(Sounds like a homework question)

You can do this in two parts, moving backwards in events. First, you can use conservation of energy to determine the velocity of the box at the instant it absorbed the bullet ( mgh = (1/2)mv^2 ). Here, "m" is the mass of the box-bullet combo.

Once you have "v" of the bullet-box combo, you can use conservation of momentum to determine what the original velocity of the bullet was
( (mass bullet-box combo)(velocity) = (mass bullet)(velocity bullet) + (mass box)(velocity box) )

Of course the initial velocity of the box is zero, so it all works out nicely.


* All of this assumes an "instant" collision between the bullet and the box.
 

1. What is an inelastic collision?

An inelastic collision is a type of collision where the kinetic energy of the colliding objects is not conserved. This means that some energy is lost during the collision, typically in the form of heat or sound.

2. How is an inelastic collision different from an elastic collision?

In an elastic collision, the kinetic energy of the colliding objects is conserved. This means that the total kinetic energy before the collision is equal to the total kinetic energy after the collision. In an inelastic collision, the kinetic energy is not conserved and some energy is lost.

3. What factors affect the amount of energy lost in an inelastic collision?

The amount of energy lost in an inelastic collision depends on the materials and properties of the objects involved, as well as the speed and angle of the collision. Objects with higher elasticity (ability to return to their original shape) will lose less energy in a collision compared to objects with lower elasticity.

4. How are the velocities of the objects after an inelastic collision determined?

The velocities of the objects after an inelastic collision are determined using the law of conservation of momentum. This law states that the total momentum of the objects before the collision is equal to the total momentum after the collision. However, in an inelastic collision, some kinetic energy is lost so the velocities of the objects will be lower after the collision compared to before.

5. Can an inelastic collision ever result in the objects sticking together?

Yes, an inelastic collision can result in the objects sticking together. This typically occurs when the colliding objects are made of the same material and have similar properties. In this case, the kinetic energy lost during the collision is converted into potential energy, causing the objects to stick together.

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