Kinetic Energy Conservation in an Explosive System

In summary, the conversation is discussing a physics question about an explosion that splits a body into two chunks. The conversation touches on the concepts of conservation of kinetic energy and momentum, and concludes that both principles still apply in this scenario. The final answer is that one chunk moves at 4 m/s while the other remains at the explosion site.
  • #1
walker
28
0
Having some problems with this question, was wondering if anyone could lend some hints/explanation.

Q.
A body of mass 8.0kg is traveling at 2.0m/s under the influence of no external agency. At a certain instant an internal explosion occurs, splitting the body into two chunks of 4.0kg mass each; 16 joules of translational kinetic energy are imparted to the two-chunk system by the explosion. Neither chunk leaves the line of the original motion. Determined the speed and direction of motion of each of the chunks after the explosion.

Are they saying the system imparts an additional 16 joules of energy from the explosion. Because the initial kinetic energy is equal to 16 joules, they could have just said kinetic energy is conserved.

I've tried using just conservation of kinetic energy and momentum and the results show that the two pieces continue on in the same direction with the same speed of 2.0 m/s, it doesn't seem like much of an explosion.

Any help with this would be great.

Thanks.
 
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  • #2
I think they are trying to say that 16 J is added to the system by the explosion (converted from potential energy (maybe chemical? not important, though)). So the kinetic energies are related by:

.5*m1*v1^2 + .5*m2*v2^2 = Ko + 16J = 32 J

and the conservation of momentum still holds:

m1*v1 + m2*v2 = M*vo = 16 Ns

That should be solvable, right?
 
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  • #3
oops, I forgot my 1/2's in the energy equation. If that's right, I get 4 m/s for one piece and the other piece stays at the explosion site.

__________

OK; fixed above too.
 
Last edited:
  • #4
That's what I came up with as well, but do you think that momentum is still conserved if the explosion imparts additional kinetic energy into the system?
 
  • #5
Yes. I think it's pretty common for momentum to be conserved while kinetic energy isn't (any collsions that are not completely elastic (read any real collision) comes to mind). Conservation of momentum should apply as long as there are no non-negligible external forces to deal with, which seems to be the case here.

(Oh, and I edited my last post, so you may want to reload the page).
 
  • #6
If you consider the centre of mass of the two particles, it is still moving at 2m/s and therefore overall momentum is conserved.
Think of it like this; the momentum of a particle will only be conserved when no external force acts on it, the explosion is an internal force, therefore overall, momentum is conserved.
 

1. What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion.

2. How is kinetic energy calculated?

Kinetic energy is calculated using the equation KE = 1/2 * m * v2, where m is the mass of the object and v is its velocity.

3. What are some examples of kinetic energy?

Examples of kinetic energy include a moving car, a rolling ball, a person running, and a swinging pendulum.

4. Can kinetic energy be converted into other forms of energy?

Yes, kinetic energy can be converted into other forms of energy, such as potential energy, thermal energy, and sound energy.

5. How does kinetic energy affect an object's ability to do work?

Kinetic energy is a form of energy that can be used to do work. The greater an object's kinetic energy, the more work it is capable of doing.

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