What is the recoil speed of the rifle?

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The discussion centers on calculating the recoil speed of a 2.0 kg air rifle after firing a 1.0 g bullet at a muzzle velocity of 150 m/s. The initial momentum of the bullet is calculated incorrectly, leading to confusion about the correct recoil speed. The correct conversion of the bullet's mass from grams to kilograms is emphasized, clarifying that 1.0 g equals 0.001 kg. The momentum equation p=mv is applied, and the correct recoil speed is determined to be -7.5 m/s, indicating the rifle moves in the opposite direction of the bullet. Overall, the approach to solving the problem is deemed generally correct despite initial calculation errors.
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Homework Statement


Kim holds a 2.0 kg air rifle loosely and fires a bullet of a mass 1.0 g. The muzzle velocity of the bullet is 150 m/s. What is the recoil speed of the rifle?


Homework Equations


p=mv


The Attempt at a Solution


p=(150)(.01) 15=2v
p=15 7.5=v
 
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Looks correct. Just note that it is -7.5m/s
 


No, it is not OK. 1.0g is not 0.01kg.

Even assuming it is, 150*0.01 is not 15.
 


I apologize wasn't what i had on my paper in a bit of rush to see if i was understanding the equation. You are absolutely right 1 g is .001kg and it multiplied by 150 is 1.5, but besides careless errors i just want 2 know am i on the right track
 


General approach seems to be OK :smile:
 

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