# Meteorite Energy Question

1. Dec 6, 2006

### Kildars

1. The problem statement, all variables and given/known data

On August 10, 1972, a large meteorite skipped across the atmosphere above western United States and Canada, much like a stone skipped across water. The accompanying fireball was so bright that it could be seen in the daytime sky (Fig. 7-24). The meteorite's mass was about 4 x 10^6 kg. Its speed was about 15 km/s. Had it entered the atmosphere vertically, it would have hit the Earth's surface with about the same speed.

(a) Calculate the meteorite's loss of kinetic energy (in joules) that would have been associated with the vertical impact.
J
(b) Express the energy as a multiple of the explosive energy of 1 megaton of TNT, which is 4.2 1015 J.
megaton TNT
(c) The energy associated with the atomic bomb explosion over Hiroshima was equivalent to 13 kilotons of TNT. To how many "Hiroshima bombs" would the meteorite impact have been equivalent?

2. Relevant equations

I'm pretty confused on how to start this one, I guess this unit I have been pretty lost the whole unit. So if someone could give me a good way of starting I would greatly appreciate it.

Last edited: Dec 6, 2006
2. Dec 6, 2006

### Staff: Mentor

What is the equation for the Kinetic Energy (KE) of a mass m moving with a velocity v? What happens to the KE when the mass is stopped suddenly like in an impact on the surface of the Earth?

3. Dec 6, 2006

### Kildars

E = 1/2mv^2

Kinetic energy goes to 0 when it hits the surface, correct?

4. Dec 6, 2006

### Staff: Mentor

Yep. Now calculate the KE of the meteorite in joules (1J = 1kg*m/s^2), and do the math for the problem. I'm kind of interested in that last answer myself.

5. Dec 6, 2006

### Kildars

/confused.

Last edited: Dec 6, 2006
6. Dec 6, 2006

### Staff: Mentor

What is the KE of the meteorite before the impact (use that equation), expressed in joules like the problem statement says?

7. Dec 6, 2006

### americanforest

Find initial KE with $$KE=\frac{1}{2}mv^2$$. This answer, assuming you use kilograms for mass and meters/second for velocity, is in Joules. Convert from Joules to Megatons by << rest of complete answer deleted by berkeman >>

Last edited by a moderator: Dec 6, 2006
8. Dec 6, 2006

### Staff: Mentor

Please do not post almost-complete answers to homework questions. It is against forum guidelines, and does not help the student to learn anything.

9. Dec 6, 2006

### americanforest

Sorry. Won't happen again.

10. Dec 7, 2006

### Staff: Mentor

Fair enough. And thanks for helping out with homework questions. The more people helping, the better.