Conservation of momentum (should be easy)

AI Thread Summary
An object with a mass of 16 kg and a speed of 19 m/s explodes in deep space, resulting in two pieces, one four times the mass of the other. The less massive piece stops relative to the observer, prompting a calculation of the kinetic energy added during the explosion. The original momentum was calculated correctly, but the final kinetic energy was miscalculated due to an error in summing the masses for momentum. The correct delta KE, after recalculating, is determined to be 722 J. The discussion emphasizes the importance of careful calculations in physics problems involving momentum and energy.
gbdusty
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An object, with mass 16 kg and speed 19 m/s relative to an observer, explodes into two pieces, one 4 times as massive as the other; the explosion takes place in deep space. The less massive piece stops relative to the observer. How much kinetic energy is added to the system during the explosion, as measured in the observer's reference frame?

I calculated the original momentum, then i calculated the final momentum. I then solved for vfinal. I got 23.75 m/s for my vfinal. But now I tried calculating delta KE and I'm getting 1624.5 J, but my homework site is telling me it is incorrect. Can someone help me out?
 
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I believe that your vfinal is correct, but you have probably made some stupid mistake with calculations at the end.
Initial kinetic energy is 0.5*16*(19)^2 and final KE is 0.5*(16/5)*4*(23.75)^2, and the difference, delta KE is 722J. Check it again!
 
Are you using the correct formula?
 
thanks i was adding both masses for the final momentum, that was my foolish mistake.
 

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